S. Subramanian et Pr. Adiga, Characterization and hormonal modulation of immunoreactive thiamin carrierprotein secreted by adult vat Leydig cells in vitro, J ENDOCR, 162(1), 1999, pp. 49-56
Leydig cells isolated from adult rats and maintained under defined conditio
ns in culture secrete a protein of molecular weight (M-r) 70 000 which is i
mmunologically similar to chicken thiamin carrier protein (TCP). Synthesis
of immunoreactive TCP by these cells is demonstrated by immunoprecipitation
of [S-35]methionine incorporated, newly synthesized proteins with monoclon
al and polyclonal antibodies to chicken TCP. The amount of immunoreactive T
CP secreted into the culture supernatant is quantitated by using a specific
radioimmunoassay. Under the influence of LH, secretion of immunoreactive T
CP is enhanced 3-fold and can be inhibited by up to 70% with aromatase inhi
bitor (1,4,6-androstatrien-3,17-dione). Cyclic AMP acts as a second messeng
er in the sequence of events involved in LH-induced elevation of immunoreac
tive TCP in Leydig cells. The effects of exogenous estradiol-17 beta and di
ethylstilbestrol are comparable in terms of stimulation of secretion immuno
reactive TCP by these cells. Tamoxifen brought about a 70% decrease in the
elevated levels of immunoreactive TCP. These results suggest that estrogen
mediates immunoreactive TCP induction in hormonally stimulated adult rat Le
ydig cells.