Gluconeogenesis from [l-14C]pyruvate in the perfused liver from fasted rats was stimulated by oleic acid as indicated by an increase in medium glucose, liver glycogen and specific activity of medium [14C]glucose. A balance of carbon from pyruvate revealed that in the presence of oleic acid 2 moles of pyruvate were utilized for each mole of glucose synthesized in contrast to a ratio 4: 1 without fatty acid. From this and 14C0, data it is concluded that oleic acid inhibited pyruvate oxidation markedly. Glucagon increased glucose formation from pyruvate but not from glycerol.Tremendous interest in the factors controlling the rate of gluconeogenesis has been shown in recent years. Long-chain fatty acids have been found to stimulate gluconeogenesis in the perfused rat liver using lactate [l] or alanine as substrate [2,3], and caprylate stimulates glucose formation in liver slices [4]. Increased fatty acid oxidation and ketogenesis have also been implicated in the i n vivo stimulation of gluconeogenesis by glucagon [5,6]. This interrelationship between increased fatty acid oxidation and gluconeogenesis has pointed to an acetyl-CoA activation of pyruvic carboxylase [7] as one of the possible control points in gluconeogenesis [S]. Recently, caprylate [9] and palmitate [lo] have been observed to decrease the oxidation of pyruvate by rat liver mitochondria, which is possibly due to an inhibition of pyruvic dehydrogenase by acetylCoA [10,11].Although glucagon has been reported to stimulate glucose production from lactate [1,12,13], pyruvate [13], fructose [13], and glycerol [14], studies of hepatic intermediates [6,12] have indicated that glucagon may accelerate gluconeogenesis a t the ratelimiting level which exists between pyruvate and phosphoenolpyruvate.The present work is a continuation and extension of the studies on the control of gluconeogenesis initiated by Struck and co-workers in our laborato-' Y [151.These workers found a stimulation of gluconeogenesis from lactate by either glucagon or oleic acid. The present studies are concerned with gluconeogenesis from pyruvate and the effect of oleic acid on this rate. The effect of glucagon on gluconeogenesis from glycerol and pyruvate has also been investigated. MATERIALS AND METHODSMale albino rats (Sprague-Dawley, Gassner, Munchen), weighing between 180 and 250 g and previously fed on laboratory chow (Altromin R., Altrogge, Lage Lippe) were fasted for 18-20 h before use.All chemicals were reagent grade unless otherwise noted. L-lactic acid and DL-carnitine chloride were from Schuchardt (Munchen) and oleic acid from Riedel-DeHaen (Seelze-Hannover). The oleic acid was vacuum distilled prior to use. Glucagon was a preparation and a gift of Eli Lilly, Indianapolis, U.S.A. (Lot Nr. 258-234, B-167-1). Sodium [1-14C]-pyruvate was obtained from Radiochemical Center, Amersham, England. All substrates were prepared as neutral solutions. Glucagon was dissolved in 1/250 N HCI.The apparatus and technique of perfusion were similar to that previously described [16,17]. The perfusin...

The quantitative relation of calcium and protein secretion was studied on the isolated perfused canine pancreas at different secretory states of hydrokinetic and ecbolic stimulation and various extracellular Ca++-concentrations. 1. Calcium and protein secretion are correlated at both ecbolic and hydrokinetic stimulation as well as by biological or synthetic secretion. 2. Enzyme-associated calcium was estimated at 35 nmol/mg protein and did not vary under differing stimulatory and secretory conditions. 3. During variable concentrations of synthetic secretin basal protein and calcium concentrations in the pancreatic juice show a hyperbolic relationship to the respective rates of fluid secretion. At flow rates beyond 3 ml/5 min the calcium concentrations asymptotically tend to 0.46 mEq/l while protein concentrations nearly decrease to zero. Moreover, the y-intercept of the regressionline correlating the calcium and protein concentrations gives with 0.48 mEq/l Ca++ additional evidence of the existence and magnitude of an enzyme-independent calcium fraction, which seems to remain constant over the whole range of secretory rates. 4. The omission of perfusate calcium does not abolish the calcium-protein correlation either at hydrokinetic or at ecbolic stimulation, but diminishes the enzyme-independent calcium fraction. 5. Enhancing perfusate Ca++-concentrations augments calcium output byt fails in stimulating enzyme secretion. It is concluded that at exclusively hydrokinetic stimulation basal secreted protein with a definite amount of chelated calcium is diluted by variable rates of pancreatic juice containing enzyme independent Ca++ at a constant concentration. During different secretory states of hydrokinetic or ecbolic stimulation the respective proportions of enzyme associated and independent calcium vary, and thus determine changes in the calcium-protein ratios. Extracellular calcium can only influence the non-protein-bound calcium fraction of the pancreatic juice presumably by diffusion from the extracellular fluid through the ductal epithelium rather than by an active secretory mechanism.

1. The kinetics of Ca++ and enzyme secretion are of corresponding pattern as well at hydrokinetic as at ecbolic stimulation. 2. Physiological respectively pathophysiologically relevant changes of perfusate Ca++ concentrations do not influence pancreatic Ca++ secretion. Extracellular Ca++ concentrations beyond 12 mEq/1 initiate an enzyme independent Ca++ secretion. 3. Hydrokinetic or ecbolic stimulated pancreatic secretion do not distinguish in calcium/protein ratio. 4. Basal and stimulated enzyme secretion of isolated perfused canine pancreas remain unaffected by increments of extracellular Ca++ concentrations even at pharmacological values. 5. The stimulated enzyme- and Ca++ secretion remain constant during hypocalcemic perfusate conditions but decrease to basal values in Ca++ free media, rapidly and completely reversible by recalcification of the perfusate. 6. The secretin stimulated volume secretion remains unchanged either by extremely hypercalcemic or Ca++ depleted perfusate conditions.

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