Age-related changes in [125I]hLH specific binding to rat interstitial cells

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Abstract
Enriched Leydig cell suspensions were prepared from rats ranging from 5-80 days of age. The cells were incubated with [125I] human LH [luteinizing hormone] in vitro, and the proportion of LH binding cells were determined by autoradiography. The proportion of 3.beta.-hydroxysteroid-dehydrogenase (3.beta.-HSD) positive cells was also determined. By Scatchard analysis and determination of grain counts of LH positive cells, an increase in LH receptors per LH binding cells with increasing age was found. LH binding cells from animals 5 and 10 days of age had few LH receptors, but more than a doubling between day 10 and day 20; a significant increase was seen between day 20 and 40, whereas only a slight increase in LH receptors per LH binding cell was seen thereafter. Scatchard analysis and grain count analysis of labeled cells gave essentially the same results. The grain count distribution showed cells distributed around low grain values in animals of all ages; a subpopulation of cells with high grain counts appeared in maturing and mature animals. Only a small fraction of LH positive cells had detectable levels of 3.beta.-HSD activity in animals 5 and 10 days of age. With increasing age the proportion of 3.beta.-HSD positive cells approached that of LH binding cells; rat interstitial cells aquire LH receptors well before any 3.beta.-HSD activity can be traced.