Growth in young rats after termination of sodium selenite exposure: studies of growth hormone and somatomedin C.

In a previous study we have shown that the growth retarding effect of selenium in infant rats occurs concomitantly with severely reduced growth hormone responses and serum somatomedin C. Furthermore, normal growth may be restored by administration of exogenous growth hormone administration. In the present study we examined the alterations after withdrawal of selenite administration in growth rate, serum growth hormone after GRF 40 injection and serum somatomedin C. Thirty-six rats were divided into 3 groups; i.e. controls, rats on continuous selenite treatment from days 21 to 63 of age and a group where selenium was withdrawn on day 42. The first 2 groups grew linearly during the experimental period, the second at a very significantly lower rate. In the third group after cessation of exposure a brief growth spurt occurred followed by a growth rate significantly different from that of the other 2 groups. The reduced GH response to GRF 40 stimulation was normalized 3 weeks after withdrawal, whereas serum somatomedin C remained at the same low level as in those rats on continuous selenite administration. There were other signs of liver lesion at day 42, i.e. elevated ALAT and reduced serum albumin, changes which became insignificant in all 3 groups at the end of the experiment. These results demonstrate that whereas stimulated growth hormone secretion was reestablished 3 weeks after termination of selenium exposure, severely reduced liver somatomedin C production persisted. An improvement in growth rate was also noted, but normal growth rate was not reached 3 weeks after discontinuation of the selenite treatment.