Changes in Testicular Steroidogenic Acute Regulatory (STAR) Protein, Steroidogenic Enzymes and Testicular Morphology Associated with Increased Testosterone Secretion in Bulls Receiving The Luteinizing Hormone Releasing Hormone Agonist Deslorelin

• Published in: Domestic animal endocrinology Vol. 15; no. 4; pp. 227 - 238
• Main Authors: Aspden, W.J, Rodgers, R.J, Stocco, D.M, Scott, P.T, Wreford, N.G, Trigg, T.E, Walsh, J, D’Occhio, M.J
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-07-1998
• Subjects: 17-Hydroxysteroid Dehydrogenases - biosynthesis; 17-Hydroxysteroid Dehydrogenases - genetics; AGONISTS; Alcohol Dehydrogenase - antagonists & inhibitors; ANIMAL PROTEINS; Animals; BLOOD PLASMA; Blotting, Northern - veterinary; Blotting, Western - veterinary; BULLS; Cattle - metabolism; Cholesterol Side-Chain Cleavage Enzyme - biosynthesis; Cholesterol Side-Chain Cleavage Enzyme - genetics; CYTOCHROME P450; Drug Implants; Enzyme Inhibitors - pharmacology; ENZYMES; Gonadotropin-Releasing Hormone - administration & dosage; Gonadotropin-Releasing Hormone - agonists; Gonadotropin-Releasing Hormone - analogs & derivatives; Gonadotropin-Releasing Hormone - pharmacology; HORMONES; HYDROXYSTEROID DEHYDROGENASE; LHRH; Luteinizing Hormone - blood; Male; MESSENGER RNA; OXIDOREDUCTASES; Peptidylprolyl Isomerase - biosynthesis; Peptidylprolyl Isomerase - genetics; Phosphoproteins - biosynthesis; Phosphoproteins - genetics; PROTEINS; Random Allocation; RELEASING HORMONES; RNA, Messenger - analysis; SECRETION; Seminiferous Epithelium - anatomy & histology; Seminiferous Epithelium - drug effects; Seminiferous Tubules - anatomy & histology; Seminiferous Tubules - drug effects; Spermatids - cytology; Spermatids - drug effects; SPERMATOGENESIS; Spermatogenesis - drug effects; Steroid 17-alpha-Hydroxylase - biosynthesis; Steroid 17-alpha-Hydroxylase - genetics; STEROID METABOLISM; STEROIDOGENESIS; TESTES; Testis - anatomy & histology; Testis - drug effects; Testis - enzymology; Testis - secretion; TESTOSTERONE; Testosterone - blood; Testosterone - secretion; Triptorelin Pamoate - analogs & derivatives
• ISSN: 0739-7240; 1879-0054
• DOI: 10.1016/S0739-7240(98)00013-7

Testosterone secretion and the expression and relative contents of steroidogenic acute regulatory (StAR) protein and steroidogenic enzymes cholesterol side-chain cleavage cytochrome P450 (P450
scc), 3β-hydroxysteroid dehydrogenase /Δ
5 → Δ
4 − isomerase (3β-HSD), and 17α-hydroxylase cytochrome P450/C
17–20 lyase (P450
17α) were determined in testicular tissues of bulls treated with a LHRH agonist. Testis morphology and spermatogenesis were also examined. In Experiment 1, bulls (30-mo-old) received no treatment (control,
n = 7) or were implanted for 10 days with the LHRH agonist deslorelin (
n = 7). Bulls were castrated on Day 10 and testis tissues prepared for Western and Northern blotting. At castration, bulls implanted with deslorelin had greater plasma testosterone (5-fold) and testis content of testosterone (10-fold) compared with control bulls. Relative content (per μg total testis protein or RNA) of StAR protein, 3β-HSD, P450
scc, and mRNA for P450
17α in bulls treated with deslorelin ranged from 3- to 6-fold that of control bulls. In Experiment 2, bulls (20-mo-old) were left untreated (control,
n = 6) or implanted with deslorelin (
n = 12) for 120 days. On Day 120, bulls were castrated and right testis tissues prepared for morphology. Testis volume and weight were increased (P < 0.01) in bulls treated with deslorelin compared with control bulls. Stereological analysis revealed that this increase occurred in all compartments (seminiferous epithelium, lumen and interstitium) studied, but was significant (P < 0.01) only for the seminiferous epithelium. Absolute numbers of round spermatids per testis were increased (P < 0.05) in bulls treated with deslorelin compared with control bulls. Increased testosterone secretion in bulls treated with deslorelin was associated with increased testicular StAR protein and steroidogenic enzymes. Bulls treated long-term with deslorelin had a faster rate of testis growth and increased daily sperm production at the end of the experiment.