Photoperiod-Mediated Increases in Serum Concentrations of Inhibin, Follicle-Stimulating Hormone, and Luteinizing Hormone are Accentuated in Adult Shortened-Scrotum Rams without Corresponding Decreases in Testosterone and Estradiol1
| Autor: | Wylie Vale, Josef K. Voglmayr, Lee M. Sanford, Bernard Robaire |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
endocrine system
medicine.medical_specialty medicine.drug_class Inhibin secretion Cell Biology General Medicine Biology Follicle-stimulating hormone Endocrinology Reproductive Medicine Estrogen Internal medicine medicine Testicular Regression Gonadotropin Luteinizing hormone Testicular Hormones hormones hormone substitutes and hormone antagonists Testosterone |
| Zdroj: | Biology of Reproduction. 49:365-373 |
| ISSN: | 1529-7268 0006-3363 |
| DOI: | 10.1095/biolreprod49.2.365 |
| Popis: | Relationships between "seasonal" changes in the secretion of gonadotropic (FSH, LH) and gonadal feedback (inhibin, testosterone, estradiol) hormones were examined in the adult ram. Eight Dorset x Leicester x Suffolk rams were kept in photoperiodcontrolled rooms for 2 yr and subjected to alternating 4-mo periods of stimulatory (8 h light) and inhibitory (16 h light) daylengths. The scrota of four rams were shortened at the outset to elevate testicular temperature and presumably impair inhibin secretion by Sertoli cells. Blood samples were collected serially from the jugular vein every 3 wk, and scrotal circumference of the four control rams was measured every 2 wk. Testicular recrudescence and regression were completed in the second month of the short- and long-day periods, respectively. Mean serum concentrations of testosterone and estradiol varied in synchrony across months (r = 0.42) and were similar between the groups of rams, except early in the short-day periods when testosterone was 50% lower in the shortened-scrotum rams because of smaller "seasonal" increases in testosterone pulse amplitude and baseline concentration. Increases in the secretion of gonadotropic hormones during testicular recrudescence were greater in magnitude (FSH) and/or of longer duration (FSH, LH pulse amplitude, and baseline LH) in rams with shortened scrota. In fact, mean FSH concentration was an average of 250% higher in the shortened-scrotum vs. the control rams throughout the last two photoperiod cycles. Mean inhibin concentration varied with month in accordance with FSH (r = 0.52) and either remained normal or was higher than usual (e.g., 55% during testicular regression) in the shortened-scrotum rams. Results underscore the complexity of gonadal regulation of LH and FSH secretion in the ram and the need to investigate the feedback role of other testicular hormones. |
| Databáze: | OpenAIRE |
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