AJP - Gastrointestinal and Liver Physiology, Vol 254, Issue 3 315-G321, Copyright © 1988 by American Physiological Society
Thyroxine effect on exocrine pancreatic development in rats
R. B. Lu, K. Chaichanwatanakul, C. H. Lin, E. Lebenthal and P. C. Lee
Children's Hospital of Buffalo, Department of Pediatrics, State University of New York 14222.
Thyroxine and glucocorticoids both play important roles in regulating the
development of mammalian tissues. The mechanisms by which they modulate the
developmental process is not fully understood. Furthermore, the interaction
between the effects of two hormones on the pancreas has not been studied in
detail. To investigate these issues, we studied the effect of thyroxine
and/or corticosterone on the development of the exocrine pancreas in normal
and adrenalectomized rats. Daily injection of thyroxine (0.1 micrograms/g
body wt) to pups starting at day 5 of age resulted in precocious increases
of exocrine enzymes in the pancreata of these pups. Hypothyroid pups,
induced by propylthiouracil, exhibited suppression of development of their
pancreatic exocrine enzymes. Replacement of thyroxine or corticosterone
alleviated the suppression of exocrine enzyme development in these pups.
Rat pups, who underwent adrenalectomy at 5 days of age, had undetectable
plasma corticosterone and exhibited similar suppression of pancreatic
enzyme development. Injection of thyroxine or corticosterone alone to
adrenalectomized pups led to normal development of exocrine pancreatic
enzymes. When both thyroxine and corticosterone were given together to
adrenalectomized pups, their pancreatic enzyme levels were found to
increase to values above those of pups treated with thyroxine or
corticosterone alone. We conclude that thyroxine has both direct and
indirect modulatory roles in the development of the rat exocrine pancreas.
Normal development of the exocrine pancreas depends on both intact adrenal
and thyroid function in the rat.
