The absorption of folic acid from segments of the small intestine of the rat has been measured in situ with tritium-labelled folic acid. The fraction absorbed was independent of concentration below 106 M but was depressed to half at 4x10-5 M.Direct measurements of fluxes showed that the mucosal -e serosal flux was about 14 times the serosal -> mucosal flux, and therefore that uptake of folic acid is an active process. In the ileum but not in the duodeno-jejunum, absorption was depressed by the presence of electrolyte. There was little difference in absorptive capacity between jejunum and ileum nor was there any significant change in animals suffering from a dietary deficiency of folic acid.

We examined carbohydrate metabolism and endocrine responses during elective abdominal surgery in nondiabetic and in insulin-treated diabetic patients. The diabetic patients were divided into two groups: those receiving preoperative subcutaneous (s.c.) insulin and those receiving continuous, low dose intravenous (i.v.) insulin infusions. Glucose, glucagon, cortisol, growth hormone, and insulin levels were measured preoperatively, intraoperatively, and for up to 6 h postoperatively. In the nondiabetic subjects glucose levels rapidly rose at initiation of surgery and continued to increase slowly, reaching a peak of 269 ± 26 (SEM) mg/dl at 60 min into the recovery period. Insulin levels also slowly increased throughout surgery, peaking at 103 ± 32.6 (SEM) uU/ml at 60 min into the recovery period, which was followed by a prompt decline in glucose levels. Glucagon levels remained relatively stable during surgery, but increased steadily during the recovery period to 300 ± 59 (SEM) pg/ml at the end of the observation period. Both cortisol and growth hormone rose during surgery, with growth hormone reaching a peak at 45 min [31.1 ± 13.8 (SEM) ng/ml], while cortisol continued to increase, plateauing during the recovery period at about 30 μg/dl. In the diabetic patients there were no differences in preoperative glucose, glucagon, cortisol, and growth hormone levels between the two treatment groups, and only the glucose level was different from the nondiabetic group. During surgery, there were trends toward lower plasma glucose levels in the early intraoperative phase in the diabetic patients receiving the continuous, low dose i.v. insulin infusion compared with those who received conventional preoperative s.c. insulin. There was no difference in the timing or magnitude of the rise of the measured hormones between the two groups. We conclude that a continuous, low dose i.v. insulin infusion at the dose used (1 U/h) is as effective in the treatment of the diabetic surgical patient as conventional preoperative s.c. insulin administration. Endocrine and metabolic responses to surgery are not different in the two forms of insulin administration.

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