CIRCULATING LUTEINIZING HORMONE AND TESTOSTERONE RESPONSE IN RAMS AFTER LUTEINIZING HORMONE RELEASING HORMONE TREATMENT

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Abstract
The relationship between the secretions of LH and testosterone after LH-RH administration was tested in entire rams. Three groups of two rams received, intravenously, 100 μg; 800 μg LH-RH in single injection; or 100 μg × 7 injections at half-hour intervals respectively and samples were collected every 10 or 20 min for 6 hours. Plasma LH and testosterone were assayed by radioimmunoassay. The quantity of LH released following 800 μg LH-RH was higher than released after 100 μg LH-RH and there was a positive correlation between the total amount of LH released after LH-RH and the amount of testosterone released. It seems probable that the pre-injection level of testosterone regulates in a quantitative manner the effect of a given dose of LH-RH. In the case of successive injections of LH-RH, the plasma LH rose to a plateau but the last two treatments failed to prevent the decline in the level of LH. This suggests that testosterone, still high at the time, directly blocked the effect of LH-RH at the level of the pituitary.

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