The effect of corticosteroids on pinocytosis in the neonate rat and ferret ileum: A morphological study.
2015-11-19T08:51:53Z (GMT) by
The rat ileum normally ceases uptake of macromolecules between 18 and 21 days of age. During this period the immature vacuolated cells on the villus are replaced by a new population of mature nonpinocytosing cells from below. This is known as ileal closure. A single intraperitoneal injection of cortisone acetate to 5 day old rats induced precocious closure within 6 days. The closure process was similar to that seen during normal ileal closure. During both normal and induced closure morphometric measurements showed that there was a gradual loss of the vacuolated cell population as one passed down the villus. This was thought to be due to a gradual increase in the degree of differentiation in the cells produced by the crypt; related perhaps to the duration of the exposure of the crypt to the closure stimulus. 10 days after cortisone acetate treatment vacuolated cells were again seen on the villus. Their distribution varied from animal to animal. sometimes covering the whole villus and sometimes only the top half of the villus. One of the possible explanations for this is discussed. Administration of corticosterone, the naturally occurring corticosteroid in the rat, to young rats failed to promote any morphological changes indicative of ileal closure at the electron microscope level. Normal closure in the ferret ileum occurs between 35 and 39 days of age, by a similar process of apparent cellular replacement as that seen during normal ileal closure in the rat. Administration, to young ferrets, of cortisone acetate at many doses up to lethal ones failed to promote any morphological changes indicative of ileal closure. The possible role of the corticosteroids in the normal closure process in the mammalian intestine and the apparent species specific effect of cortisone acetate are discussed.