INTESTINAL CONTRACTILE PROTEINS AND NUCLEIC-ACIDS IN RESPONSE TO ADRENALECTOMY, THYROIDECTOMY AND SURGICAL STRESS

Objective: To investigate the importance of the endocrine environment on intestinal smooth muscle protein metabolism. Design: Thyroidectomiz ed (Tx), adrenalectomized (ADX), appropriate sham-operated (sham-Tx an d sham-ADX) and unoperated young adult male Wistar rats were fed on or dinary laboratory chow ad libitum and killed on day 7. Whole intestina l and seromuscular layer preparations were made from the jejunum and l arge intestine. Tissues were assayed for contractile proteins and nucl eic acids. Results: In Tx rats, whole jejunum tissue mean wet weights were reduced by 21% compared with sham-Tx and by 12-23% compared with the unoperated group. Thyroidectomy induced significant reductions in the total content of all protein fractions of the whole jejunum and je junal seromuscular layer compared with sham-Tx and unoperated groups. No significant changes in the large bowel seromuscular layers were obs erved. There were significant reductions in total RNA and DNA content in whole jejunum tissue. Adrenalectomy significantly reduced small int estinal weight. Total protein was unaltered in all protein fractions o f jejunal tissues and no changes in total RNA or DNA content were obse rved; however, significant reductions in whole jejunal DNA occurred. N o overt changes were observed in any of the derived parameters in the small bowel, except for a significant reduction in the protein:DNA rat io in whole jejunal tissue. Sham-Tx or sham-ADX had no significant eff ects on tissue wet weights, total protein, total RNA and DNA content c ompared with the unoperated group. Derived parameters, RNA:protein, RN A:DNA and protein:DNA ratios also failed to show any statistically sig nificant changes. Conclusions: Marked reductions in intestinal contrac tile protein content and concentration were found. The most profound e ffects were observed following thyroidectomy and jejunal tissues appea red to be the most sensitive. The loss of total protein and especially the contractile apparatus represented by the myofibrillar protein fra ction could well explain small intestinal motility disorders commonly encountered in endocrine dysfunction.