Lecture 3. Reproductive Endocrinology. (Sep 30, 2008)

Transcription

1 Lecture 3 Reproductive Endocrinology (Sep 30, 2008)

2 Major achievements that speed up the development: 1. The anterior pituitary controls the function of the gonads. 2. Gonads produce steroid hormones that alter the function of the reproductive tissues. 3. Females experience reproductive cyclicity and that ovulation is predictable.

3 4. Worldwide success of AI was due to the understanding of sperm physiology during 1940s to 1950s. 5. Development of the techniques for XYsperm separation, ET, cryopreservation, and electronic estrous detection, etc. 6. PGF2αregulated the length of the estrous cycle in females (1960s). 7. Development of RIA for hormone analysis (1960s).

4 Radioactive hormone competes with the same hormone from the blood. The amount of radioactivity is inversely proportional to the concentration of unlabeled hormones (=hormone conc.) Radioimmunnoassay (RIA) analysis of hormone concentration

5 Radioimmunoassay (RIA) vs. Enzyme-linked immunosorbent assay (ELISA) RIA: sensitive, radioactive, required more training ELISA: less expensive, no radiation, no safety hazard issues, minimal training required (p.124, Fig 5-19) Primary Ab Secondary Ab Typical enzymes used are alkaline phosphotase, horseradish peroxidase, β-galactosidase.

6 Hormones: Endocrinology Metabolism Reproduction

7 Endocrine Glands Hypothalamus Pineal gland Adrenal gland Ovary Pituitary Uterus Placenta Testes (in bull) Thyroid Pancreas

8 Apocrine (gland): Exhibiting that type of glandular secretion in which the free end of the secreting cell is cast off along with the secretory products accumulated therein (e.g., mammary and large sweat glands in hairy regions). A coiled, tubular gland whose secretory cells accumulate their products on their apical surfaces that are then pinched off to become the secretion, as in the mammary glands. Eccrine (gland): Any of the numerous small sweat glands distributed over the body's surface that produce a clear aqueous secretion devoid of cytoplasmic constituents and important in regulating body temperature.

9 Endocrine Gland A ductless gland Secretes substances (hormones) into blood or lymph that affect cells elsewhere in the body The secretion does not involve loss of tissue or provide energy to the target cells.

10 Endocrine Endo: from the Greek endon ; within Crine: Krinein ; to release Endocrinology The study of chemical communication systems that provide the means to control a huge number of physiologic processes (integration): A science involves in chemical integration of the body.

11 Endocrinology The study of chemical communication systems that provide the means to control a huge number of physiologic processes (integration): A science concerned with chemical integration of the body. Focused on Animal (re)production Human medicine

12 Please read: Chapter 5 Regulation of Reproduction: Nerves, hormones & target tissues

13 Female The puerperium and lactation Parturition Fetal attachment and gestation Early embryogenesis and maternal recognition of pregnancy Ovulation & fertilization Male Am I out of here? Cyclicity Regulation of reproduction Tract function Spermatogenesis Regulation of reproduction Tract function Puberty Puberty Prenatal development Prenatal development

14 Stages Gonads Sex behaviors CNS Hypothalamus Endocrine system Portal system pituitary Steroids Polypeptides (GFs, activins, inhibins) Feedback loops (-/+) or servomechanism CNS Endocrine system Paracrine/autocrine Immune system Chronology of changing concepts on regulation of mammalian reproduction

15 Hormones Greek verb: to excite, and encompass Signaling molecules produced by the endocrine gland (glandular cells) Secreted into the internal milieu Acts on target cells, tissues or organs at a place other than where it is produced. Acts as a catalyst (needs receptors)

16 Hormones are chemical substances produced in one part of the body that diffused or is transported in another area where it influences activity and tends to integrate component parts of the organism. Bayliss and Starling (1902)

17 Other forms of hormone regulation Paracrine: a cell secrets a compound acts on neighboring cells (a small distance) Autocrine: a cell utilizes the compound it produces by itself Epicrine: hormones pass through gap junction of adjacent cells without entering extracellular fluid. Intracrine: the regulatory molecules remain and effective within the cell Neurocrine: Hormones diffuse through synaptic clefts between neurons (neurotansmitters)

18 Classification of hormones base on: 1. Source of origins 2. Type of functions 3. Biochemical classifications (mode of action)

19 [Classification & Properties of Hormones] A. Source of origin: site of production; glandular origins Hypothalamic hormones: GnRH, oxytocin, neuropeptides (<20 AAs) [STH-RF, STH-IF, CRH, TRF, PRF, PIF] Pituitary hormones: gonadotropins +.. Gonadal hormones: affect the functions of the hypothalamus, pituitary, reproductive tracts (E2, P4), and 2 sex characteristics

20 [Classification & Properties of Hormones] B. Type of functions/action 1. Primary hormones of reproduction (FSH, LH, E2, P4) 2. General metabolic hormones (thyroxin, insulin, STH): Secondary hormones of reproduction

21 [Classification & Properties of Hormones] C. Chemical structures Polypeptides: hypothalamic, GnRH Proteins/glycoproteins: pituitary, gonads Steroids: gonadal, adrenal hormones Fatty acids: many sources, prostaglandins Modified amino acid: thyroid hormones, melatonin

22 Pyroglu His Trp Ser Tyr Gly Leu R CH NH 3 Arg O HN C C HC O R Peptide Bond Pro Gly R CH NH NH2 COO- Peptide hormones can not be given orally. Amino acid sequence of GnRH

23 Prostaglandins (fatty acid, arachidonic acid derivatives) PGF 2α PGE 2 (Figs. 5-11; P114)

24 Characteristics of Hormones (1) Act in minute quantities ( ) (2) Have short half-lives in general (differs between water soluble and insoluble) (3) Bind to specific receptors (4) Regulate intracellular biochemical reactions

25 Pheromones Another class of substances directly influences reproductive processes. Substances are secreted to the outside of the body. Volatile & detected by olfactory system (vomeronasal organ) Nasopalatine (incisive) ducts P Functions to influence the onset of puberty, the identification of estrus by the males, other behavioral & physiological traits.

26 Functions of the Endocrine (Integration) Nervous & endocrine systems interact to initiate, coordinate and regulate reproductive functions. Nervous system: acts within seconds Endocrine system: acts in minutes or hours Incorporation of the immune system