In vitro progesterone production of corpus luteum in pregnant Mongolian gerbils (Meriones unguiculatus)

Abstract

The present study was conducted to determine the in vitro progesterone (P4) production by Mongolian gerbil (Meriones unguiculatus) corpus luteum (CL) on days 9, 18 and 22 of pregnancy in comparison with rat CL on days 9 and 16. The culture medium of one CL per well of a 96‐well plate was changed after 4 h incubation and the CL were further cultured for 24 h. The P4 in serum and in the medium were measured by enzyme immunoassay system. Gerbil CL weight measured after 24 h incubation was at the same level for all 3 days of pregnancy and significantly different from that of the rat CL for the 2 days of pregnancy. The serum P4 level in gerbils was high in early pregnancy and decreased in advanced days of pregnancy. In contrast, the P4 in rats was higher in the latter half of pregnancy. In vitro P4 production by a single CL after 4 h incubation decreased significantly during the days of pregnancy in both the gerbil and the rat. P4 values produced by the gerbil CL for 24 h incubation were significantly higher than after 4 h incubation in all 3 days of pregnancy, however, there was no difference between the two incubation time groups in the rat. In vitro P4 production by CL correlated well with the serum P4 level on the 3 days of pregnancy in the gerbil. In the rat, however, the relationship was inversed between the two parameters. The correlation in this experiment suggested that CL is the sole source of P4 for the maintenance of the gerbil pregnancy, with the result of abortion after an ovariectomy on day 20 of pregnancy as described in our previous report.