Endocrinology, Vol 108, 2406-2408, Copyright © 1981 by Endocrine Society
Effect of the alpha subunit of equine LH on the FSH induced cAMP production in rat seminiferous tubule cells
BB Aggarwal, H Papkoff and P Licht
Previous observations from our laboratory have shown that equine LH can
suppress the FSH induced cyclic AMP production in rat seminiferous tubule
cells in vitro. The present investigation was carried out to determine the
effect of various subunits in this system. The ratios (w/w) of subunits to
equine FSH tested was 1:3, 3:1 and 30:1 with a standard dose of 0.3
microgram of the FSH. It was noted that equine LH- beta was not effective
up to a 10 microgram concentration in inhibiting the cyclic AMP production
induced by equine FSH. Under these conditions, equine LH-alpha suppressed
the FSH activity in a dose dependent manner. However, alpha subunits
derived from several other species of LH were without any effect on FSH
action. Histidine modified derivative of equine LH and its alpha subunit,
both of which lack biological activity in the rat Leydig cell assay for LH,
were found to be inactive as inhibitors of the equine FSH response. Thus,
these results show that the suppressive effect of equine LH on FSH action
in the rat seminiferous tubule is a function of the equine LH alpha
subunit.
