A high-resolution genetic map of mouse chromosome 5 encompassing the reeler (rl) locus.

Using interspecific crosses between BALB/c and Mus spretus (SEG) mice, the murine reeler (rl) gene was mapped to the proximal region of chromosome 5 between the hepatocyte growth factor gene (Hgf) and the D5Mit66 microsatellite. The following order was defined: (centromere)-Cchl2a/Hgf-D5Mit1-D5Nam1/D5-Nam2 -rl/D5Mit61-D5Mit72-Xmv45-Htr5a- Peplb-D5Nam3-D5Mit66. Estimated distances between reeler and the nearest flanking markers D5Nam1 and D5Mit72 are 1.5 and 1.0 cM, respectively (95% confidence level), suggesting that the region could be physically mapped using a manageable number of YAC clones.

Reappraisal of the role of insulin on sodium handling by the kidney: f1fect of intrarenal insulin infusion in the dog.

Since several studies suggest that increased insulin levels may induce antinatriuresis, the present work was undertaken to determine whether a physiological increase in insulin levels in blood perfusing the kidney may exert direct effect on kidney function, and more specifically on sodium reabsorption. To this end, insulin was infused directly into one renal artery of 10 anaesthetized dogs at the rate of 4 mU min-1 for a period of 90 min. The contralateral kidney was infused with saline alone, to provide reference values. Insulin level in the renal vein of the insulin-infused kidney went up from 1.4 +/- 0.9 before to 30.6 +/- 7.1 microU ml-1 after 90 min of insulin perfusion. There was no significant effect on renal plasma flow, glomerular filtration rate and renal uptake of substrates or oxygen between ipsi- and contralateral kidney. The fractional excretion of sodium was likewise unaffected, since it averaged at the end of insulin infusion 0.41 +/- 0.11% vs. 0.50 +/- 0.14% for the contralateral saline infused kidney. Even if one may assume that the baseline low insulin concentrations promote tubular sodium reabsorption, the results of the present study suggest that a moderate hyperinsulinaemia is without any additional effect on renal sodium handling.

Stabilization of left ventricular function with D-(-)-3-hydroxybutyrate after coronary occlusion in the intact dog.

The D-(-) isomer or natural form of 3-hydroxybutyrate (D-(-)-3OHB) is a readily used energy substrate. Studies on anesthetized intact dogs in our laboratory have demonstrated that raising the arterial level of D-(-)-3OHB to 1 mM enhances the ketone uptake not only by the normal, but also by the acutely ischemic myocardium, though at a lower rate. Whether this moderate rise in arterial D-(-)-3OHB does modify the time course of left ventricular (LV) function during acute regional ischemia remains unsettled. In the present study, 13 anesthetized intact dogs with occluded left anterior descending (LAD) coronary artery (balloon catheter) were infused with D-(-)-3OHB as the L-(+)-arginine salt at a rate of 20 mumol/kg/min i.v. for 90 min, starting 40 min after the LAD occlusion. Arterial D-(-)-3OHB rose to 1.1 mM. Arterial pH was not modified. By comparison with the decline observed in 13 saline-treated ischemic dogs, the ketone treatment significantly stabilized the time course of LV peak positive dP/dt and output per minute. This effect was not attributable to the simultaneous infusion of arginine since it was not observed with equimolar infusions of this amino acid alone in eight additional ischemic dogs.

In vivo effect of the D-(-) isomer or natural form of 3-hydroxybutyrate on initial release of lactate dehydrogenase from the acutely ischaemic myocardium.

D-(-)-3-hydroxybutyrate, the isomer found in the circulation and in the urine of diabetic patients, generally is believed to be the physiologically important form of 3-hydroxybutyrate [10]. Little is known concerning the effects of an elevated plasma level of the D-(-) isomer of 3-hydroxybutyrate upon the acutely ischaemic heart. Using anaesthetized intact dogs with a balloon catheter inserted into the proximal part of the left anterior descending coronary artery (LAD), we have recently demonstrated that a 1 mM ketonaemia induced with the arginine salt of D-(-)-3-hydroxybutyric acid reduces the uptake of non-esterified fatty acids (NEFA) in the myocardial area distal to the inflated balloon [4]. The question arises as to whether the concomitant increase in ketone uptake in this area could be detrimental to the acutely ischaemic myocardium. Indeed, a previous study on isolated coronary ligated hearts from normal rats has shown that the rate of release of lactate dehydrogenase (LDH) during the first 90 min of ischaemia can be enhanced by replacing glucose (11 mM) in the perfusion fluid with either albumin-bound palmitate (0.9 mM) or sodium DL-3-hydroxybutyrate (10 mM) as the sole energy substrate [11]. This would suggest that the ketone might be as deleterious as its metabolic precursors for membrane integrity in the acutely ischaemic myocardium. In the present report, we examine the effect of arginine D-(-)-3-hydroxybutyrate on LDH release from ischaemic myocardium in our in vivo preparation. The dogs were treated with lidocaine in order to minimize the frequency and, hence, the adverse metabolic effects of ectopic beats.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effects of the D(-)isomer of 3-hydroxybutyrate on cardiac non-esterified fatty acid uptake and oxygen demand induced by norepinephrine in the intact dog.

The effects of ketosis on the norepinephrine-induced high rates of cardiac uptake of non-esterified fatty acids (NEFA = free fatty acids = FFA) and oxygen consumption were studied in anesthetized intact dogs. After a control infusion of norepinephrine (500 ng/kg.min into the left ventricle), the D(-) isomer or natural form of 3-hydroxybutyrate was infused intravenously as the arginine salt at rates of 20 mumol/kg.min in group A (10 dogs) and 80 mumol/kg.min in group B (10 dogs) and a second norepinephrine infusion was superimposed on the ketone treatment. At the time the effects of the second catecholamine infusion were measured, the arterial 3-hydroxybutyrate concentration averaged 1.2 +/- 0.1 mM in group A and 8.3 +/- 0.4 mM in group B, and the cardiac uptake of the ketone amounted to 17.4 +/- 0.6 and 35.8 +/- 5.3 mumol/min.100 g, respectively. Relative to the control norepinephrine infusion, the arterial NEFA concentration was reduced to 88 +/- 4% in group A and to 62 +/- 8% in group B, but the cardiac uptake of NEFA was significantly more depressed, to 65 +/- 7% in group A and to 35 +/- 8% in group B. These changes were not observed in ten non-ketotic animals under repeated norepinephrine infusion. Thus, ketosis inhibited the norepinephrine-stimulated uptake of NEFA, presumably through (1) a lowered availability of NEFA from arterial blood, attributable to a reduction of extracardiac lipolysis, and (2) competition of 3-hydroxybutyrate with NEFA for metabolism by the myocardium in the face of still high arterial NEFA concentrations, 1.7 +/- 0.1 mM in group A and 1.1 +/- 0.2 mM in group B. In both groups, the lowering of the contribution of NEFA to cardiac metabolism was associated with a reduction of the estimated oxygen demand per beat (ratio of cardiac oxygen consumption/min to the pressure-rate product), while the pressure response to norepinephrine was not modified. There was no evidence for abnormal cardiac function.

Release of cyclic adenosine 3',5'-monophosphate in the coronary venous blood during an intracoronary infusion of adenosine.

The effect of adenosine on the release of cyclic adenosine 3',5'-monophosphate (cyclic AMP) in the coronary venous blood was examined in 30 anaesthetized intact dogs. Adenosine was infused into the left anterior descending coronary artery (LAD) at a rate of 150 nmol . min-1 and coronary venous blood was sampled in the great cardiac vein (GCV), near the outflow site of the veins accompanying the LAD. Significant coronary veno-arterial differences in cyclic AMP plasma level were observed before and during the infusion. The myocardial blood flow supplied by the LAD increased from 56 +/- 3 to 237 +/- 23 ml . min-1 per 100 g myocardium and the rate of cyclic AMP release in the venous blood near the origin of the GCV increased from 15.2 +/- 3.0 to 104.8 +/- 29.5 pmol . min-1 per 100 g myocardium. The adenosine-induced release of cyclic AMP did not result from an action of the substance on the platelets in the coronary circulation since adenosine concentration comparable to that achieved in the LAD did not modify the cyclic AMP plasma level of arterial blood in vitro. It is concluded that the released nucleotide originated essentially in cardiac structures, i.e. the myocardial and/or coronary cells. The results support in vitro studies suggesting that cyclic AMP is involved in the metabolic regulation of coronary blood flow by adenosine.

Adenosine-induced release of cyclic adenosine 3',5'-monophosphate from the left ventricle in the anaesthetized intact dog.

1. The influence of adenosine on the release of cyclic adenosine 3',5'-monophosphate (cyclic AMP) from the heart was examined in twenty-two anaesthetized intact dogs. The animals were pre-treated with propranolol and vagotomized. The rate of nucleotide release from the left ventricle was determined as the product of the left ventricular myocardial plasma flow and the coronary veno-arterial difference in plasma nucleotide concentration. 2. Adenosine was infused into the left ventricle during three successive 15 min periods at rates of 25, 50 and 100 n-mole/kg. min, respectively. The mean blood pressure in the ascending aorta was prevented from falling by inflating a balloon placed into the thoracic aorta. The measurements were performed before the infusion and at the 10th min of each infusion period. The values given are means +/- S.E. 3. During the 45 min infusion of adenosine at increasing rate, the cyclic AMP concentration in arterial plasma increased from 7.0 +/- 0.3 to 14.0 +/- 0.9 p-mole/ml. The nucleotide was released from the left ventricle at rates increasing from 48.2 +/- 7.1 to 206.5 +/- 56.2 p-mole/100 g. min while the left ventricular myocardial blood flow increased from 127 +/- 6 to 399 +/- 33 ml./100 g.min. The oxygen consumption of the left ventricle was not modified. 4. When adenosine was infused at a rate of 100 n-mol/kg.min, the thorax was opened and the apex of the heart and the left atrial appendage were removed for nucleotide assay. The cardiac cyclic AMP concentration did not differ from that observed in control dogs. 5. The results suggest that cyclic AMP is likely to be involved in the membrane and cellular events underlying the relaxant effect of adenosine on the coronary smooth muscle. The lack of change in cardiac cyclic AMP concentration, as determined by whole tissue extractions, is consistent with a study by others showing that, under normoxic conditions, cyclic AMP is released from a small, compartmentalized fraction of the cyclic AMP content of the heart. The elevation of the plasma nucleotide concentration could result from adenosine effects on various cell systems or organs, in addition to the observed release from the heart.

Isoprenaline-induced release of cyclic adenosine 3',5'-monophosphate by the left ventricle in the anaesthetized intact dog.

The ability of the heart to release cyclic adenosine 3',5'-monophosphate (cyclic AMP) in the coronary venous blood was examined in closed-chest anaesthetized dogs before and during an infusion of isoprenaline. Before the infusion, no difference was observed between the cyclic AMP plasma levels in the aortic and coronary sinus blood. During the infusion, significant coronary veno-arterial differences in nucleotide concentration were observed despite a considerable elevation of the cyclic AMP plasma level in the aortic blood.