Effect of long-term infusion of an LH-releasing hormone agonist on testicular function in bulls.
Continuous administration of LH-releasing hormone (LHRH) agonists is an effective method of suppressing testosterone secretion in the male. The effect of the LH-releasing hormone (LHRH) agonist, buserelin, administered to bulls by constant infusion from osmotic minipumps was studied. In one experiment with four treated and one control bull, 109 micrograms buserelin/day were administered for 22 days. Immediately after implantation, serum testosterone concentrations rose from below 35 nmol/l to 35-105 nmol/l, and all four buserelin-infused bulls showed increased testosterone secretion during the treatment period. After removal of the minipumps, testosterone concentrations decreased to pretreatment levels. In a second experiment bulls were infused for 42 days (four treated and one control), and identical results were obtained. Testosterone secretion was stimulated (52-87 nmol/l serum) during the entire treatment period. These results demonstrate that conditions for stimulation of the pituitary-testicular axis may vary between species. Infusion of low doses of LHRH-agonists in bulls has an extended stimulatory effect without immediate desensitization of gonadotrophin release.
D000818:Animals; D002064:Buserelin / Q000008:administration & dosage* / Q000494:pharmacology; D002417:Cattle; D004343:Drug Implants; D008297:Male; D013737:Testis / Q000187:drug effects / Q000378:metabolism*; D013739:Testosterone / Q000097:blood / Q000378:metabolism*; D013997:Time Factors
D004343:Drug Implants; D013739:Testosterone; D002064:Buserelin