The effect of exogenous steroids and steroid inhibitors on IgG transmissions in young rats.

The transmission of labelled IgG by the proximal small intestine was assessed in 16- and 18-day-old rats. Closure had commenced by 18 days and in some animals was well advanced by this age. The injection of large doses of cortisone acetate, hydrocortisone sodium succinate, deoxycorticosterone acetate and corticosterone induced precocious closure of the small intestine by 16 days; and all but the latter steroid also induced precocious cell replacement in the ileum. Maternal deprivation for about 18 h daily led to closure of the proximal small intestine but did not induce precocious replacement in the ileum. The injection of metopirone, aminoglutethimide and ACTH resulted in partial closure of the proximal small intestine but did not induce precocious cell replacement in the ileum. Maternal deprivation for about 8 h daily produced a similar result.