pregnant mare's serum gonadotrophin

Transcription

1 by Restratin f the LH surge and vulatin insulin in allxan-diabetic immature rats treated with pregnant mare's serum gnadtrphin Hward J. Kirchick, P. Landis Keyes and Billy E. Frye Divisin fbilgical Sciences, The Reprductive Endcrinlgy Prgram, Center fr Human Grwth and Develpment and The Department fphysilgy, The University fmichigan, Ann Arbr, Michigan 489, USA Abstract. Immature allxan-diabetic rats injected with pregnant mare's serum gnadtrphin (PMSG) d nt vulate and the LH surge is absent. In the present studies we have examined the effects f several insulin treatments n the LH surge and vulatin in allxan-diabetic rats. Rats were made diabetic by injectin f allxan n day 4 f age. Only thse rats with fasting bld glucse cncentratins exceeding 8 mg/ ml n day 7 were cnsidered diabetic. PMSG was injected n day. Rats received insulin either by injectin (,, 4 r 6 IU/ g/day; Ultralente B.I.D.) r by subcutaneus implants (Alzet smtic minipumps;.8 r.4 IU/day). Nne f the diabetic rats withut insulin treatment vulated. Sme f the animals in each insulin treatment grup vulated, hwever, the percentage f animals vulating was highly variable frm experiment t experiment when the insulin was given by injectin. When insulin was administered by smtic minipump, the results were mre cnsistent, with at least 6% f the rats vulating in each experiment. LH surges This wrk was presented in part at the 6th Annual Meeting f the Endcrine Sciety (Abstract 4), Miami Beach, Flrida. It was supprted in part by a grant frm the Hrace H. Rackham Schl f Graduate Studies, The frm the NIH University f Michigan, and by a grant (HD-77). Supprted by a Training Grant (HD-748) frm the NIH. Present address: Department f Cell Bilgy, Baylr Cllege f Medicine, Hustn, Texas 77. Address requests fr reprints t: P. Landis Keyes, Reprductive Endcrinlgy Prgram, Center fr Human Grwth and Develpment, The University f Michigan, Ann Arbr, Michigan 489, USA. were fund n the afternn f presumed pr-estrus (day ) in diabetic insulin-treated rats which vulated. In cnfirmatin f previus results, rats withut insulin treatment did nt have LH surges. Althugh the site f insulin actin has nt been determined, these data indicate that the LH surge mechanism in the immature PMSG-treated rat is insulin-dependent. Experimental diabetes mellitus interrupts repr ductive functins in rats and insulin therapy has been reprted t restre gnadtrhin respnses such as varian weight gain (Farina et al. 97; Liu et al. 97) and varian chlesterl depletin (Farina et al. 97). Attempts t restre estrus cycles in diabetic rats by insulin therapy have met with variable success (Chieri et al. 969; Kim et al. 96; Lawrence & Cntpuls 96). Althugh insulin may partially amelirate the derangement in cyclicity, the effects f insulin therapy n the pre-vulatry LH surge are unknwn. We have recently reprted that allxan-induced diabetes in PSMG-treated immature rats results in anvulatin, which is due t the absence f the LH surge, rather than t a lack f varian respnsiveness t gnadtrphins (Kirchick et al. 978). Insulin in jectins restred vulatin in diabetic animals, but subsequent attempts were less successful. The pur pse f this research was t determine the efficacy f insulin therapy in the restratin f the LH surge, vulatin and bdy weight gain in diabetic rats. Dwnladed frm Biscientifica.cm at //8 :6:PM

2 Animals Materials and Methds Immature -day ld female rats (Hltzman Cmpany) were hused three t a cage in a temperature cntrlled rm with 4 h f light daily (lights n at 6. h). The animals were fed ad libitum (Purina rat chw) except during perids f fasting when the animals were allwed access t water nly. At 6. h n day 4 f age, the animals were injected sc with either allxan ( mg/kg bdy weight in citratephsphate buffer ph 4) r with the buffer vehicle nly fllwing an 8 h fast. At 9. h n day 7 f age,. ml f bld was taken frm each animal by heart puncture under light ether anaesthesia fllwing a 6 h fast. The bld was assayed fr glucse (see belw). Animals with a fasting bld glucse exceeding 8 mg/ ml ( mm) were cnsidered diabetic. This level f bld glucse is apprximately -fld the level fund in cntrl rats. The mean ± SD fasting bld glucse fr all animals classified as diabetic in these studies was ± 7 mg/ ml with the grup means ranging frm 54 t 75 mg/ ml. The mean ± s value fr all f the cntrl animals was 9 ± mg/ ml with the grup means ranging frm 7 t 4 mg/ ml. Between. and. h n day f age, the animals were given a sc injectin f PMSG ( IU/ g bdy weight, Ayerst). Fasting bld glucse determinatin. Bld glucse was measured using a mdificatin f the semi-micr glucse xidase methd (Wrthingtn Bi chemical Cmpany). All reagents were prepared accrd ing t the instructins and sdium hydrxide was used in place f barium hydrxide as indicated as an ptin in the instructins. The prcedure was mdified t yield a final cncentratin f.5 ml f sample in a ttal vlume f. ml. The reactin was allwed t g t cmpletin by incubating the assay tubes at 7 C fr h. The samples were transferred t cuvettes and were read in a Zeiss PMQ spectrphtmeter system at 4 nm. The sensitivity f the assay was abut.5 mg/ ml and bth the intra- and inter-assay cefficients f variatin were apprximately.48%. Insulin replacement In several f the experiments belw, animals were checked peridically fr ketnuria using Ketstix (Ames Cmpany). Ketnuria registering + r + was cnsid ered slight while ketnuria registering + r 4+ was cnsidered severe. If an animal was ketnuric, it was assumed that it was als ketnaemic. Injected insulin was Ultralente (Eli Lilly Cmpany; lu/ml; ph 7.4), a lng-acting suspensin. The insulin administered by smtic minipump was unmdified in sulin which is a ph 7.4 slutin f zinc insulin crystals which are nt mdified t increase half-life. The Alzet smtic minipump (Alza Crpratin) is an implantable device which delivers substances at relatively cnstant rates (Theeuwes & Yum 976; Frankel et al. 979). We assumed a pumping rate f 4 ul/d. Therefre, by filling the pump with a slutin f IU/ml f insulin, we expected.4 IU f insulin t be delivered by the pump each day. We did nt urselves check the accuracy f the pumping rate. The pumps were filled and immediately inserted sc. Ovulatin in allxan-diabetic rats treated with insulin by injectin (Table ) Fur experiments were perfrmed. In the first experi ment, a grup f diabetic rats (la) received insulin sc (.5 IU/ g/injectin), nce in the mrning and again in the evening, beginning n the evening f day 7 f age and cntinuing until the evening f day. Anther grup f diabetic rats (lb) received the same dse f insulin but nly n day f age (ttal f tw injectins). Diabetic rats in the secnd experiment were injected B.I.D. with either r IU/ g/injectin frm the evening f day 7 f age until the mrning f presumed pr-estrus (day ). In the third and furth experiments, diabetic rats were injected with insulin ( IU/ g/injectin, B.I.D.) frm the evening f day 7 f age until the mrning f day. Each experiment included a grup f nn-diabetic cntrl rats and a grup f diabetic rats injected with the insulin vehicle nly. The rats were killed, weighed, and examined fr va n the mrning f presumed estrus (day ) as described previusly (Kirchick et al. 978). In the third experiment, nnfasting bld glucse cncentratins were determined in several animals fllwing the mrning injectin f insulin r vehicle n day 9 f age t examine the respnse t an injectin f insulin. LH surge in allxan-diabetic rats treated with insulin by injectin Animals were injected with insulin ( IU/ g/injectin) as described fr experiments 4 abve. The animals were bled by heart puncture under light ether anaesthe sia at either., 5., 8. r. h n presumed pr-estrus and the sera were frzen until assayed fr LH. LH surge and vulatin in allxan-diabetic rats treated with insulin by smtic minipump Three experiments were perfrmed. In each experi ment, cntrl, diabetic, and diabetic insulin-treated rats were used. The rats receiving insulin were implanted sc n day 7 f age with Alzet smtic minipumps (ne pump per animal) which were calculated t deliver.4 IU/day f unmdified insulin. In the first experiment anther grup f diabetic insulin-treated rats received dses calculated t be.8 IU/d via smtic minipump. Dwnladed frm Biscientifica.cm at //8 :6:PM

3 Cntrl and diabetic animals in the secnd and third experiments were implanted sc with empty minipumps. In the first tw experiments (Table ), the animals were killed, weighed, and examined fr va n presumed estrus as described previusly (Kirchick et al. 978). In the third experiment, bld was taken frm animals frm each grup by heart puncture under light ether anaesthesia at., 5., 8. and. h n pre sumed pr-estus and the serum was frzen until assayed fr LH (Fig. 4). Each animal was sampled nly nce. All f the diabetic rats which were sampled at 8. and. h were checked fr vulatins the fllwing day t crrelate the incidence f vulatin with the LH surge. In additin, grups f cntrl, diabetic, and diabetic insulin-treated rats (.4 IU/day) were checked fr nnfasting bld glucse levels t determine the efficacy f insulin treatment (Fig. ). Animals frm each grup were bled by heart puncture under light ether anaesthesia every 4 h fr 4 h n days 8-9 and -. Radiimmunassayfr serum LH Serum LH was assayed using the A4 antiserum as described previusly (Kirchick et al. 978, 979). The reference standard used was NIH LH-RP (. X NIH LH-S). Statistical methds Multiple cmparisns were made using analysis f vari ance (ANOVA) except where nted, in which case the cmparisns were made using Student's i-test. Radiim munassay results were analysed using a cmputer pr gram based n the assay statistics described elsewhere (Midgleyetal. 969; Duddlesn et al. 97). Table. Final bdy weights and the incidence f vulatin in diabetic rats treated with insulin by injectin. Experiment Dse f insulin (per g per day) Day bdy weight (g) Per cent vulating (%) Cntrl 4 / 5/5 5/5.9 ±. 98. ± ± ± 7. 8 Diabetic 4 / 4/ ± ± ±. 6. ±5. Diabetic + insulin la lb a b 6/5 6/5 6/4 7/ / 9/9 IU fr 4 days IU fr day 4 IU fr 4.5 days 6 IU fr 4.5 days IU fr 4.5 days IU fr 4.5 days 7. ± ± ± 6." 96.9 ±.9* 74.7 ±.9>4 76. ±.6." The rats were injected with PMSG n the mrning f day f age and were killed n day. Insulin was injected twice daily beginning n the evening f day 7 f age except fr experiment lb in which insulin injectin began n the mrning f day. The cmparisns belw were made using ANOVA. Mean ± sem. Significantly different frm crrespnding cntrl grup (P <.5). Significantly different frm crrespnding cntrl grup (P <.5). 4 Significantly different frm crrespnding diabetic grup (P <.5). Dwnladed frm Biscientifica.cm at //8 :6:PM

4 E 4 Insulin"'. I S (IIU/IOOgJ. m - Cntrl I Animal O--O Diabetic (N Insulin)-I Animal A-A Diabetic (Insulin)- Animals,- CL~ JÍ Insulin (IIU/IOOg) Time f Day (h) Fig.. Bld glucse levels f several animals fllwing injectin f insulin r insulin injectin vehicle. The animals were injected at 8. h n day 9 f age and were bled at intervals until 9. h. Table. Final bdy weights and the incidence f vulatin in diabetic rats treated with insulin via smtic minipump. Experiment (initial/final) Dse f insulin (per g per day) Per cent vulating (%) Cntrl 4/4 6. ±. 7. ± ± 4. Diabetic 4/4 5/4 8. ± ± ±4.4 Diabetic + insulin la 5/5 lb 6/4 5/5 /.8 IU.4 IU.4 IU.4 IU 9.4 ±.4. ± 5.." 74. ± 5.>4 8.9 ± The rats were injected with PMSG n the mrning f day f age day. Insulin was delivered by smtic minipumps which were implanted evening f day 7 f age. The cmparisns belw were made using ANOVA. Mean ± sem. Significantly different frm crrespnding cntrl grup (P <.5). Significantly different frm crrespnding cntrl grup (P <.). 4 Significantly different frm crrespnding diabetic grup (P <.5). and were killed n sc n the 69 Dwnladed frm Biscientifica.cm at //8 :6:PM

5 - Results Ovulatin in allxan-diabetic rats treated with insulin by injectin The data frm the fur experiments are given in Table. Nne f the untreated diabetic rats vu lated, whereas all but ne f the cntrl animals sme f the insulin- vulated. In each experiment, treated rats vulated. As the dse f insulin was increased, the final bdy weights f the insulintreated diabetic rats was always significantly greater than the respective means fr the diabetic rats withut insulin treatment (P <.5), with the ex ceptin f the first experiment. In the secnd experiment, the mean final bdy weight f the diabetic insulin-treated rats was nt different frm that f the cntrl rats. In all ther cases, hwever, 95 p 9 85 m E.8 I CD 75 UJ >- CD E 5 *M 4' 5' *M-MIDNIGHT Begin..._A--- il / / Diabetic Diabetic + Insulin I-FASH M M M M M 6' 7' 8' 9' Day f Age ' Fig.. Grwth curves f cntrl rats, diabetic rats, and diabetic rats treated with insulin via smtic minipump. Animals treated with insulin were implanted sc n the evening f day 7 with Alzet smtic minipumps which delivered.4 IU/day f unmdified insulin. All animals were fasted fr apprximately h between days 6 and 7. Each pint represents a mean grup fr the rats in the secnd smtic minipump experiment (n 4, 4, and = 5 fr cntrl, diabetic, and diabetic plus insulin, respec tively). there was a significant difference (P<.). Al thugh the bdy weight gain increased with in creasing dses f insulin, s did the mrtality rate. Althugh the mean final bdy weights f the diabetic insulin-treated rats in the third and furth experiments are very similar, 9% f the insulintreated rats vulated in the third experiment whereas nly 44% f the insulin-treated rats vu lated in the furth experiments. Fig. shws the bld glucse levels f several animals fllwing either insulin r vehicle injectin. In the tw diabetic insulin-treated rats, the bld glucse cncentratins returned t pre-injectin levels within 7 h after the injectin. Fr a brief perid f time, these animals were smewhat hypglycaemic. LH surge in allxan-diabetic rats treated with insulin by injectin At 8. and. h (during the perid f the LH surge in cntrl rats), nly 5 ut f diabetic insulin-treated rats shwed elevated serum LH cncentratins, at 8. h and at. h. The mean serum LH cncentratins f the diabetic insulin-treated rats with serum LH abve ng/ml (apprximately twice basal cncentratins; reference standard is NIH LH-RP.X NIH LH-S) are 6 ng/ml at 8. h and 5 ng/ml at. h. These values cmpare t 478 and 64 ng/ml, respectively in the cntrl rats. Because f statistical cm the small sample sizes, meaningful parisns cannt be made between the tw grups. LH surge and vulatin in allxan-diabetic rats treated with insulin by smtic minipump. The data regarding vulatin in the three experi ments are shwn in Table. All f the cntrl animals vulated. Nne f the untreated diabetic rats vulated, whereas at least 6% f the insulintreated diabetic rats vulated in each f the experi ments. In all cases, the mean final bdy weight f the insulin-treated grups were significantly greater than the means f the respective diabetic grups withut insulin treatment (P <.5), ex cept fr the insulin-treated grup receiving.8 IU/day which was nt different frm the untreated diabetic grup. Similarly, all f the diabetic insulintreated grups had significantly lwer mean final bdy weights than the cntrl grups (P <.). Only ne f the 7 animals treated with insulin via smtic minipump died during the curse f the experiments. Dwnladed frm Biscientifica.cm at //8 :6:PM

6 Day 8 Day 9 Day Day _J_i_I_I------! TIME OF DAY (hurs) Fig.. Nn-fasting bld glucse levels in cntrls rats, diabetic rats, and diabetic rats treated with insulin via smtic minipump. The animals treated with insulin were implanted sc n the evening f day 7 f age with Alzet minipumps which delivered.4 IU/day f unmdified insulin. Beginning at 6. h n days 8 and, bld was drawn frm each rat at 4-h intervals fr 4 h. Each pint represents a grup mean (n = 4, 4, and 5 fr cntrl, diabetic, and diabetic plus insulin, respectively). Fig. is a plt f the grwth curves fr the rats in the secnd experiment. In the animals treated with insulin by smtic minipump, bdy weight begins t plateau by the end f the experiment. Fig. cntains the plts f the bld glucse cncentratins f the three grups n days 8 9 and. These rats were nt fasted prir t sampling. On days 8-9 (4-8 h after insulin treatment was initiated), the bld glucse levels in the insulin-treated grup were nly slightly ele vated ver thse f the cntrl grup, and were less than thse f the untreated diabe substantially tic grup. Hwever, between the days f presumed pr-estrus and presumed estrus, the insulintreated grup had bld glucse cncentratins nly slightly lwer than thse f the untreated diabetic grup. The results f the experiment examining the LH surge in diabetic rats treated with insulin via sm tic minipumps are illustrated in Fig. 4. A LH surge was bserved in each diabetic insulin-treated rat which vulated (8 f vulated and had LH surges), hwever, the surges appeared smewhat smaller than in the cntrl animals. The. h mean serum LH cncentratin in the diabetic insulin-treated grup was significantly less than that f the cntrl grup (P <.), but there was n significant difference at 8. h. In the fur insulin-treated animals which did nt vulate, serum cncentratins f LH were nly slightly elevated. Incidence f ketnuria In the abve experiments nly 5% f the un treated diabetic rats displayed any ketnuria, and less than 5% had severe ketnuria. In diabetic rats treated with insulin by injectin, 75% f the ani mals displayed ketnuria and 5% had severe ketnuria. By cntrast, in the diabetic rats treated with insulin by smtic minipump, % f the rats had detectable ketnuria but f the rats had severe ketnuria. Discussin The data presented here indicate that insulin treat ment in diabetic rats is capable f restring the LH surge and vulatin. Hwever, the degree f suc cess f the treatment is variable and, in the case f treatment by injectin, very unpredictable. Where- 7 Dwnladed frm Biscientifica.cm at //8 :6:PM

7 c 6 r 4 x 8 _i E CO CO 6 4 '/ Diabetic Insulin (vultrs) W Diabetic + Insulin (nn-vultrs) 5 8 Time f Day(h) a --»Di'abetic Fig. 4. Serum LH cncentratins n the afternn f presumed pr-estrus in cntrl rats, diabetic rats, and diabetic rats treated with insulin via smtic minipump. The animals were injected with PMSG n day f age. On day, rats frm each grup were bled at either., 5., 8., r. h. Each pint represents a grup mean ± SEM. The mean serum LH cncentratin f the diabetic insulin-treated rats which vulated was significantly lwer than that f the cntrl grup at. h (P <.), but was nt different at ther times. Statistical cmparisns were made using Student's i-test. There were 6 rats in each grup at each time. The reference standard used was NIH LH-RP (.X NIH LH-S). as Ultralente insulin is a lng-acting suspensin in man, its physilgical actin is apparently very shrt-lived in rats, as indicated by the rapid return t hyperglycaemia (Fig. ) after injectin f a dse f insulin equivalent t abut 7 IU in an adult f 7 kg. The high mrtality rate assciated with the higher dses is mst likely a result f severe hyp glycaemia since even the lwer dse results in hypglycaemia. Althugh the lw dse yields a better survival rate, and verall, a higher per cent f animals vulating, the results are highly variable. The reasns fr this variability in respnse are unknwn. Hwever, a pssible explanatin is that intermittent perids f hypglycaemia may nt be cnducive t the generatin f an LH surge. Unfrtunately, we cannt assay serum insulin accurately since the sera f insulin treated rats cntain bvine, prcine, and rat insulins which d nt run parallel in ur radiimmunassay. Hw ever, bld glucse levels n days 8 9 are rela tively cnstant (Fig. ) allwing fr fluctuatins due t feeding, which suggests that the serum insulin cncentratins are als relatively cnstant. Since the bld glucse levels described abve are near cntrl values, it appears that what wuld be a pharmaclgical dse f insulin in man (7 IU/day/7 kg), is a physilgical dse in rats. Clearly, the bld glucse levels using the smtic minipumps are mre stable than thse btained by insulin injectins. One prblem with the use f the minipumps is that the pumping rate des nt increase with increasing bdy weight. Therefre, the effective dse f insulin decreases as bdy weight increases (Table ), the effects f which can be seen by the increasing cncentratins f bld glucse ver the curse f the experiment (Fig. ). Further, the data in Fig. suggest that the diabetic insulin-treated rats grw rapidly t a certain weight, after which the amunt f insulin being delivered by the pump is prbably sufficient merely t maintain that weight. Althugh the verall success in restring vula tin and the LH surge using the smtic mini pumps is nt much greater than by injectin, there is mre cnsistency frm experiment t experi ment, and a lwer mrtality rate assciated with the use f the smtic minipumps. These effects are likely t be related t the mre cnstant levels f serum insulin achieved using the minipumps. The data n ketnuria prvide further evidence The increase in and severe ketnuria bserved in rats fr the efficacy f the minipumps. bth slight treated with insulin by injectin is puzzling, but may be due t the temprary hypglycaemia (and pssibly resultant mbilizatin f lipids as an alter nate fuel surce) which ccurs fllwing each injec tin. Only a slight increase in the incidence f mild ketnuria was bserved in rats treated with insulin by minipump, while severe ketnuria was cm pletely eliminated. In a recent study (Kirchick et al. 979) we fund that the respnse f the pituitary t gnadtrphin-releasing hrmne is attenuated in diabetic rats. Hwever, the mechanisms by which the diabe tic state affects pituitary sensitivity t gnadtrphin-releasing hrmne are unknwn and may be cmplex. Our data suggest that at least three cnditins related t diabetes culd pssibly be eliminated frm cnsideratin. The first cnditin Dwnladed frm Biscientifica.cm at //8 :6:PM

8 experiments experiment is ketnaemia. Mst f the diabetic rats were nt ketnuric yet did nt vulate. Furthermre, ne f ketnuric diabetic insulin-treated rats the severely was amng thse that vulated. The secnd cndi tin is hyperglycaemia. Even thugh animals re ceiving insulin by smtic minipump were hyperglycaemic n presumed pr-estrus and presumed estrus (Fig., right panel), a large percentage f these animals vulated. Thirdly, there are reprts in the literature linking the nset f puberty with the attainment f sme minimum bdy weight (Frisch & Revelle 97, 97). It might be argued therefre, that the diabetic rats did nt vulate because they had nt reached a minimum critical bdy weight. Our data d nt supprt this cnten tin since animals f cmparable bdy weights at estrus vulate nly if insulin is given (cmpare bdy weights in Table, diabetic vs diabetic plus insulin and ). - In summary, we have fund that insulin treat ment in diabetic rats can restre the LH surge and vulatin. We have als presented evidence which suggests that ketnaemia, hyperglycaemia, and re duced bdy weight are nt respnsible fr anvulatin in diabetic rats. The exact site f insulin actin regarding the restratin f reprductive func tins has nt been determined, but ur previus wrk (Kirchick et al. 978, 979) wuld implicate the pituitary and/r hypthalamus. References Chieri R A, Pivetta O H & Fglia V G (969): Altered vulatin pattern in experimental diabetes. Fértil Steril : Duddlesn W G, Midgley A R Jr & Niswender G D (97): Cmputer prgram sequence fr analysis and summary f radiimmunassay data. Cmput Bimed Res 5: 5-7. Farina J M S, Chieri R A, Basabe J C & Fglia V G (97): Respnse t gnadtrpins in mature and immature diabetic female rats. Fértil Steril : Frankel B J, Schmid F G & Grdsky G M (979): Effect f cntinuus insulin infusin with an 7-day 'minipump' implantable in the diabetic Chinese hamster. Endcrinlgy 4: Frisch R E & Revelle R (97): Height and weight at menarche and a hypthesis f critical bdy weights and adlescent events. Science 69: Frisch R E & Revelle R (97): The height and weight f girls and bys at the time f initiatin f the adlscent grwth spurt in height and weight and the relatinship t menarche. Hum Bil 4: Kim J N, Runge W, Wells L J & Lazarw A (96): Effects f experimental diabetes n the ffspring f the rat. Fetal grwth, birth weight, gestatin perid and fetal mrtality. Diabetes 9: Kirchick H J, Keyes P L & Frye B E (978): Etilgy f anvulatin in the immature allxan-diabetic rat treated with pregnant mare's serum gnadtrpin: absence f the prevulatry luteinizing hrmne surge. Endcrinlgy : Kirchick H J, Keyes P L & Frye B E (979): An explana tin fr anvulatin in immature allxan-diabetic rats treated with pregnant mare's serum gnadtrpin: reduced pituitary respnse t gnadtrpin-releasing hrmne. Endcrinlgy 5: Lawrence A M & Cntpuls A N (96): Reprductive perfrmance in the allxan diabetic female rat. Acta Endcrinl (Kbh) : Liu F T Y, Lin H S & Jhnsn D C (97): Serum FSH, LH and the varian respnse t exgenus gnadtrpins in allxan diabetic immature female rats. End 9: crinlgy Midgley A R Jr, Niswender G D & Rebar R W (969): Principles fr the assessment f radiimmunassay methds (precisin, accuracy, sensitivity, specificity). Acta Endcrinl (Kbh), Suppl 4: Theeuwes F & Yum S I (976): Principles f the design and peratin f generic smtic pumps fr the de livery f semislid r liquid drug frmulatins. Ann Bimed Eng 4: 4-5. Received n June rd, 98. Dwnladed frm Biscientifica.cm at //8 :6:PM