Term
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Definition
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Term
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Definition
| The study of endocrine glands and their products(hormones). Endocrine glands are ductless glands that secrete their product into the blood, where it is carried to some target organ/tissue to exert an effect. |
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Term
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Definition
| An organic chemical that exerts a biological influence on some target organ or tissue. Hormones cause changes through: Inhibiting, Exciting, Inactivating, Coordinating |
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Definition
| Water soluble, amino acid based, bind to cell surface receptor, binding triggers a "second messenger" system that transmits the signal to the interior of the cell. Prolacting, Oxytocin, Somatotropin. |
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Definition
| Soluble in organic solvents, cholesterol based, bind to internal receptors in the cell cytoplasm, hormone-receptor complex becomes activated and is translocated to the nucleus. Estrogen, Progesterone, Testosterone, Glucocorticoids. |
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Definition
| Downward regulation of some action of a target organ. PIH |
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Definition
| Upward regulation of some action of a target organ. FSH, TSH |
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Definition
| Competitive binding with another hormone, reducing or eliminating original effect. Epinephrine, oxytocin |
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Definition
| Affecting the release of some other hormone. LHRH |
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Definition
| Coordination of all hormone release (direct and indirect). |
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Term
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Definition
| Adrenocorticotropic Hormone |
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Term
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Definition
Primary Forms: 17β Estradiol, Estrone
Functions in the cow
• Maturation of the follicle
• Regulation of FSH, LH, PRL
• Initiate preparation of uterine lining
• Induction of Progesterone receptors
• Promotion of cervical fluid secretion
• Induction of cylical differentiation of vaginal cells
• Essential for mammary gland development
Estrogens are predominant during the follicular phases of the estrous cycle |
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Term
| Progestagens (progestrone) |
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Definition
Primary forms: 17,20 α-OH Progesterone
Functions in the cow
• Completion of uterine preparation
• Inhibition of sperm activity
o Secretions form the cervix
• Essential for lobulo-alveolar development
Progesterogens are predominant during the luteal phases of the estrous cycle |
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Term
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Definition
• In cell culture, if P is removed and E supplemented, some ductal growth occurs. Likewise, if E is removed and P supplemented, some alveolar development occurs. When both are present, even in sub-optimal amounts, total development is improved.
o Reduced P: limited duct, alveolar growth
o Reduced E: limited duct, alveolar growth
o Reduced E+P: moderate development |
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Term
| Hormones necessary for lactation |
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Definition
• For maximal development of the ruminant mammary gland and initiation of lactation:
o Estrogen (ducts and alveolar tissue)
o Progesterone
o Adrenal Steroids (controlled via release of ACTH) Gluccocorticoid. ACTH stimulates production of Adrenal Steroids.
o Prolactin (necessary to turn on protein synthesis-casein, enzymes)
o Growth Hormone (necessary to grow and mature animal, move nutrients as appropriate for lactation, lactation) |
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Term
| Adrenal Steroids (Cortisol, corticosterone) |
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Definition
• Produced by adrenal cortex under the influence of ACTH
• Functions
o Initiation and Maintenance of Lactation
o ^protein breakdown
o ^glycogenesis (sugar building)
o ^blood glucose
o Affects water balance |
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Term
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Definition
• Essential for initiation of milk production
• PRL stimulates Casein synthesis
• PRL/GH very similar arrangement
o Compete for binding sites
• Small hormone- molecular weight ~23,000
• Peptide hormone
• Release under control of 2 hormones from hypothalamus: PRH, PIH |
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Term
| Induction of Lactation (Generalized Scheme) |
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Definition
1. Initially treat with E and P to stimulate further mammary development.
2. Inject reserpine after steroid treatment is finished. This hormone blocks the action of PIH (Prolactin Inhibiting Hormone)
a. Inhibiting a PRL inhibitor=^PRL in circulation
3. Dexamethazone is then given approximately 7 days after steroid has ceased.
a. Stimulates glucocorticoid release
b. Approximates “stress” hormone levels seen in natural calving |
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Term
| Induction of Lactation (Timing for Treatments) |
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Definition
• Steroids (E,P) usually given 2x/d for 7 days
• Hormones dissolved in ethanol and injected subcutaneously
• Milking initiated 2-3 weeks after last injection
o Hormone treatment induces a “lag” time before milk production can occur. |
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Term
| Conclusions regarding Endocrinology |
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Definition
• Interaction of hormones is critical. It is impossible to view one hormone alone except in vitro (in the lab).
• Nervous system- not important for normal mammary growth and development, but essential to continue established lactation.
o Suckling stimulus- milk letdown, PRL release |
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