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Some of these discrepancies could be due in part to a pulsatile pattern of relaese which has been described for LH both in adult (Katongole, Naftolin and Short, 1971) and young bulls (Gombe et al., 1973 ;Thibier, 1975). They could arise also from insufficient blood samplings or number of animals studied.This confusing situation in the bull contrasts with our knowledge in the sheep in which the prepubertal period is associated with a pulsatile pattern of LH followed by a decrease in the level after puberty, whereas testosterone increases linearly (Foster, 1974 ;Courot, de Reviers and Pelletier, 1975).Thus, in an attempt to clarify the endocrine changes around puberty the concurrent patterns of plasma LH and testosterone were followed in Charolais calves from birth till one year of age.

Summary. Different radioimmunoassays of testosterone (T) dehydroepiandrosterone (DHA) and 5 a-dihydrotestosterone (5 a-DHT) were investigated for ram plasma.Specificity of the antisera, lack of noticeable binding in plasma, very low levels of other androgens allow direct plasma RIA for DHA and T by the double antibody technique. The levels obtained by this simplified method are in agreement with those found after extraction alone, after extraction and celite chromatography and after quantification with a completely different technique such as gas chromatography.The within assay variabilities for T and DHA were 4.7 p. 100 and 4.6 p. 100 respectively but vary with the level of steroid in plasma. The inter assay variabilities of T were 9.5 p. 100 and 3.2 p. 100 for 1.5 and 11.6 ng/ml of plasma respectively. The antiserum for 5 a-DHT have a specificity such that, even after celite chromatography some androgens (5 p-DHT) may interfere. However determinations of 5 u/5 !-DHT amounts are possible.The physiological validations of direct plasma T and DHA RIA were studied in various conditions. The DHA plasma variations are similar to those of T in Ram from birth to puberty, but the levels are lower. DHA plasma levels show a seasonal variation as does testosterone. Variations within 24 hrs of these two androgens were in synchrony.The direct plasma T and DHA assays are useful and inexpensive tools to characterize ram testicular function.Introduction.