Pancreatic Insulin Secretion Following Intrapancreatic Infusion of Amino Acid

Abstract

Both protein ingestion and amino acid infusion are known to stimulate insulin secretion. The mechanism of this response has been attributed to increased plasma amino acid concentration. The present studies were undertaken to determine whether this-secretory response is due to a direct effect of amino acids on the islet cells or whether it is mediated through some other indirect mechanism. Accordingly, pancreatic infusion studies were conducted to help resolve this question.Casein hydrolysate (1 gm.) infused into the pancreaticoduodenal artery of dogs for one-half hour provoked an immediate secretion of insulin into the portal vein. Femoral arterial insulin concentration also rose within five minutes, although hyperglycemia was not observed until the end of the infusion. An insulin response of similar magnitude was achieved by pancreatic glucose infusion (1 gm.). Simultaneous administration of epinephrine (30 /ig.) inhibited the insulin responses to both glucose and amino acid. Combined infusion of casein hydrolysate and glucose (0.5 gm. each) produced a greater insulin response than the sum of the individual responses, suggesting glucose-amino acid synergism. Intraportal infusion of casein hydrolysate produced no significant insulin response in either portal venous or femoral arterial plasma.These studies surest t W thp insulin response associated with ingested or parenteral protein represents a direct amino acid effect on the islets of

Regulation of Insulin Release by Pancreatic Glucagon

“…30 Since we have noted these from intrapancreatic infusion of casein and glucose as well as glucagon, we have attributed them to the nature of the insulin-secretory stimulus employed. 6 The insulin rebounds were particularly prominent when epinephrine was infused into the pancreas in either the presence or absence of casein or glucose, and were again observed in the present studies one hour after combined glucagon and epinephrine infusion (table 4).…”

“…for one-half hour. 6 Intrapancreatic infusion of epinephrine alone produced hyperglycemia without insulin release in our previous studies, whereas intraportal epinephrine caused both hyperglycemia and insulin response. A larger amount of epinephrine (ioo y.g.)…”

“…Recent work with arginine infusion in humans suggests also that glucagon is not responsible for the amino acid stimulus to insulin secretion, 25 and our previous experiments lend support to the primary nature of the islet response to intrapancreatic amino acid concentration. 6 The potent insulin-releasing effect of glucagon escaped the inhibiting effect of epinephrine (table 4). The same amount of epinephrine (30 fj.g.)…”

Plasma Levels of Prolactin, Growth Hormone, and Insulin in Sheep Following the Infusion of Arginine, Leucine and Phenylalanine

“…The recovery curve had a slope of 0.96, a correlation coefficient of 0.99 and an intercept of + 0-06. 4. Parallelism between the reference standard, LER-1O5O-C2-3 ovine GH, NIH-GH-B15 and dilutions of sheep plasma ( Fig.…”

“…(Endocrinology 9 1 : 205, 1972) T HE INFUSION of amino acids results in an increase in plasma levels of both growth hormone (GH) and insulin (Ins) in several species (1)(2)(3)(4)(5)(6). It has been postulated that the increased GH and Ins serves a physiologic role in stimulating the incorporation of amino acids into protein after feeding when plasma levels of amino acids are elevated.…”