HISTOMORPHOLOGY, OLH AND HCG RECEPTORS, AND TESTOSTERONE SECRETION IN-VITRO IN RAMBOUILLET RAMS FROM LINES IN WHICH FEMALES HAD BEEN SELECTED FOR LOW OR HIGH REPRODUCTIVE RATE

The objective of this study was to determine whether gross or histomor phological components of the testes, capacity and dissociation constan ts (K-d) of testicular oLH and hCG receptors, and gonadotrophin-stimul ated testosterone secretion in vitro differed among Rambouillet rams f rom lines selected for low or high female reproductive rate and from r ams of a random-bred control line. Lines had been selected for approxi mately 20 years. Data were collected from 22-month-old rams during the late breeding season. Rams among lines did not differ (P > 0.05) in g ross testicular characteristics or most histomorphological characteris tics. However, the percentage volume of interstitial vascular tissue w as greater (P < 0.05) for rams from lines selected for low female repr oductive rate than for rams from lines selected for high female reprod uctive rate. Receptor sites per Leydig cell and binding capacities of oLH and hCG receptors per testis, per gram of parenchyma, and per mill igram of membrane protein did not differ (P > 0.05) among lines. The K -d values for oLH and hCG receptors did not differ (P > 0.05) among li nes; however, receptor sites per Leydig cell, capacities of testicular parenchyma to bind gonadotrophin and K-d values were higher (P < 0.05 ) for oLH than for hCG receptors. Total oLH- and hCG-stimulated testos terone secretion in vitro did not differ (P < 0.05) among lines. In co nclusion, selection for or against reproductive rate in Rambouillet ew es has not altered gross or most histomorphometric characteristics of the testes of male offspring, with the exception that selection agains t reproductive rate increased the proportion of testicular volume occu pied by vascular tissue within the interstitium. Furthermore, selectio n has not altered total oLH- and hCG-stimulated testosterone secretion in vitro or the affinity and capacity of oLH and hCG receptors of the testes of male offspring.