Summary. The pancreaticoduodenal and portal venous blood flows were recorded electromagnetically in anaesthetized dogs. Blood glucose and IRI were measured in the arterial, portal, and peripheral venous as well as in the intestinal venous blood. By a mathematical model the actual net IRI output of the whole pancreas was estimated. Under basal conditions it is 10.2 + 2.4 mU/min (n = 30; 26 kg mean body wt.). After i.v. glucose injection, IRI output is rapidly enhanced. The biphasic nature of this reaction was unequivocally demonstrated by consideration of the ratio IRI output : blood glucose. Pancreaticoduodenal blood flow increases transiently in relation to the increased blood glucose concentration. The IRI secretion rate is well correlated with the blood glucose concentration and to the amounts of glucose or of blood reaching the whole pancreas. It is also correlated with the portal IRI concentration. The overall peripheral venous or arterial IRI concentrations are correlated with the IRI secretion rate, but not in all individual experiments. The different phases of IRI output (basal rate, stimulated output 1-10 min and 10-60 min) show no influence on each other, nor are they correlated with the peripheral IRI concentration area. Basal IRI output is negatively correlated with the glucose assimilation constants. These constants or the peripheral BG areas, however, are independent of the stimulated IRI output rate. However, both the assimilation constants and the peripheral BG areas are related to the peripheral IRI concentration areas. Hepatic uptake of insulin and dynamics of pancreatic blood flow seem to contribute considerably to the estimated correlation pattern.

Blood flow through the superior pancreaticoduodenal artery of anaesthetized dogs increases immediately after an i.v. glucose load and parallels to glycemia, but not to insulin output. Flow of superior mesenteric, and femoral arteries as well as of portal vein are also enhanced after rapid i.v. injections of glucose or mannitol. Extent and duration of all flow increases are dose-dependent and strongly related to the alterations of arterial plasma osmolality (maximum increase 24 mosmoles/kg). Heart rate, mean arterial blood pressure, and hematocrit remain unchanged after the first test minute. There is a considerable decrease of peripheral vascular resistance in the circulatory regions investigated. Flow through aorta ascendens is augmented for a short time. Possible mechanisms of vasodilatation are reflexes produced by osmoreceptors and/or local effects of osmolality on the tonus of vascular muscle. Within the physiological range pancreatic perfusion does not determine the amount of insulin released.

In conscious trained dogs (Alsatians) the IRI-concentration in the peripheral venous blood after oral administration of glucose increases when the blood glucose is still unchanged. After one or two peaks during the first 20 min IRI increases parallel to the blood sugar increase. In relation to the intravenous injection of glucose the IRI maximum after oral administration occurs earlier. Furthermore the ratio of the IRI to blood sugar areas is raised. Without any blood sugar change the IRI concentration after oral application of tap water increases with one or two peaks. These peaks correspond to the first peaks after oral administration of glucose. These findings are discussed in the sense of a "feed-forward" of insulin secretion after feeding via N.vagus as well as via enterohormones. More attention should be payed to the IRI course during the early phase of the oral glucose tolerance test. Mdcanisme de la sdcrdtion d'insuline apr~s administration orale de glucose. I. Ddroutement multiphasique de la mobilisation de l'insuline apr~s administration orale de glucose ehez le chien dveiUg. JDiffdrences de comportement apr~s administration intraveineuse R~sumd. Chez des chiens-bergers 6veill6s et entraln6s, apr~s administration orale de glucose, la concentration d'IRI dans le sang veineux p6riph6rique augmente ddj~ alors que la glyc6mie n'a pas encore chang6. Apr~s un ou deux pies durant les ring4 premieres minutes, I'IRI augmente parall~lement au glucose sanguin. Comparativement h l'injeetion intra-veineuse de glucose, le maximum d'IRI, apr~s administration orale, se produit plus tSt. De plus, le quotient des surfaces d'IRI et de glyc6mie est 61ev6. Sans aucun changement du glucose sanguin, la concentration d'IRI augmente avec un ou deux pics aprSs administration orale d'eau potable. Ces pics correspondent aux deux premiers pics aprbs administration orale de glucose. Ces r6sultats sent discutds dans le sons d'une s6crdtion d'insuline pr6cddant la digestion via N.vague et via entdrohormones. I1 faut aceorder plus d'attention ~ l'6volution d'IRI durant la premiere phase du test de tol6rance au glucose par voie orale. Der Mechanismus der Insulinmobilisierung nach oraler Glucosegabe. I. Mehrphasigkeit der lnsulinmobilisierung nach oraler Glueosegabe beim wachen Hund und Differenzen zum Verhalten naeh intravenSser Glucoseinje]ction Zusammenfassung. Bei waehen trainierten Sch/~ferhunden steigt die Insulinkonzentration im peripheren Venenblut nach oraler Glucosegabe schon zu einem Zeitpunkt an, da die Glyk/imie noch nicht ver/indert ist. Nach Durchlaufer~ yon 1 oder 2 Gipfeln in den ersten 20 mill tritt der Anstieg ein, der parallel dem Blutzuckergipfel verl/~uft. Im Verh/~ltnis zur intraven6sen Glucosegabe liegt das erste IRI-Maximum nach oraler Verabf..olgung zeitlich friiher. Auch ist der Quotient aus IRI-Ubersehreitungsfl/iche und Blutzuckeriiberschreitungsfl/~che erh6ht. Ohne daI3 es zu einer Blutzuckerver/~nderung kommt, steigt auch nach oraler Gabe yon Leitungswasser die IRI-Konzentration 1-oder 2gipflig an. Diese Gi...

After feeding intact conscious dogs 1000 g mashed meat, peripheral venous immunoreactive insulin activity (IRI) increases before any enhancement of amino nitrogen concentration. This course of IRI is paralleled by a decrease of free fatty acids. Meal feeding in dogs, whose pancreatic juice is completely diverted from the gut by a fistula, is followed by a similar IRI increase without a distinct enhancement of amino nitrogen. In oesophagus fistula dogs, sham-feeding meat in 9 out of 15 experiments results in a considerable early IRI increase which is correlated with a small but a significant decrease of blood glucose and free fatty acid concentrations. In these tests there was no amino nitrogen alteration either.