Relation between fertility and adrenal growth after mating in the bank vole, Clethrionomys glareolus

The relationship between adrenal status and fertility in primiparous female bank voles, Clethrionomys glareolus, was examined. Out of 68 primiparous females, killed 4.5 or 6 days postcoitum, only 36 were pregnant. The pregnant ones had significantly larger adrenals than the nonpregnant ones. The nonpregnant females also had smaller ovaries, but the presence of corpora lutea proved that ovulation had occurred. Similarly, only 5 out of 11 females, mated with vasectomized males, were pseudopregnant with large corpora lutea, 6 days postcoitum. The remaining ones had ovaries similar to those in the other nonpregnant females. The pseudopregnant females had significantly larger adrenals than the nonpseudopregnant. This relationship between fertility and adrenal growth is unexpected, as in previous experiments an increase in adrenal weight has been shown to take place in direct reponse to mating, in the absence of ovaries and embryos.