A rise in glomerular filtration rate (GFR) during saline infusion increases outer medullary more than cortical metabolic rate. To determine whether other GFR-increasing agents have a similar effect, renal metabolic rates were estimated by the heat-production technique during infusion of glycine or glucagon. Glycine and glucagon increased GFR by 17 +/- 2 and 32 +/- 2%, renal blood flow (RBF) by 34 and 21%, and outer medullary metabolic rate by 42 +/- 3 and 59 +/- 4%, respectively. Cortical metabolic rate rose by 7 +/- 1% during glucagon, and it increased by 29 +/- 2% during glycine infusion, suggesting a stimulation unrelated to sodium reabsorption. To determine whether glucagon influenced renal metabolism independent of its GFR-increasing effects, vasodilation was achieved by ureteral or suprarenal aortic constriction. Glucagon was without effect on RBF, GFR, and metabolic rate, but infusion of acetylcholine still raised RBF. We conclude that glucagon increases GFR by dilating vascular segments participating in autoregulation, and that energy-requiring NaCl reabsorption in the outer medulla is increased secondary to increased delivery of NaCl.

Large conductance calcium and voltage‐activated potassium channels (BKC a) are transmembrane proteins, ubiquitously expressed in the majority of organs, and play an active role in regulating cellular physiology. In the heart, BKC a channels are known to play a role in regulating the heart rate and protect it from ischemia–reperfusion injury. In vascular smooth muscle cells, the opening of BKC a channels results in membrane hyperpolarization which eventually results in vasodilation mediated by a reduction in Ca2+ influx due to the closure of voltage‐dependent Ca2+ channels. Ex vivo studies have shown that BKC a channels play an active role in the regulation of the function of the majority of blood vessels. However, in vivo role of BKC a channels in cardiovascular function is not completely deciphered. Here, we have evaluated the rapid in vivo role of BKC a channels in regulating the cardiovascular function by using two well‐established, rapid‐acting, potent blockers, paxilline and iberiotoxin. Our results show that BKC a channels are actively involved in regulating the heart rate, the function of the left and right heart as well as major vessels. We also found that the effect on BKC a channels by blockers is completely reversible, and hence, BKC a channels can be exploited as potential targets for clinical applications for modulating heart rate and cardiac contractility.

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Metabolic Rate in the Dog Kidney. Effect of Mersalyl, Chlorothiazide, Ethacrynic Acid and Furosemide. Scand. J. d i n . Lab. Invest. 23, 317-330, 1969. The initial rate of temperature rise during arterial occlusion was measured with fine thermocouples placed in the kidney of anesthetized dogs for estimation of local metabolic rate. Experimental evaluation of the necessary assumptions indicated the method to be applicable in the cortex and outer medulla. Since renal metabolism seems mainly determined by tubular reabsorption of sodium, the method can be used to localize the natriuretic action of diuretics. Mersalyl reduced metabolic rate per unit tissue volume of the outer medulla to 65 96 of control without significant reduction in the cortex, indicating inhibition of sodium transport in the loops of Henle. Chlorothiazide lowered cortical metabolic rate t o 76 % of control, with no change in outer medulla, indicating an action in the convoluted tubules. Ethacrynic acid and furosemide acted mainly in the loops of Henle, as indicated by reduction of outer medullary metabolic rate to 21 and 32 "lo of control values respectively. Cortical metabolic rate fell to 78 and 85 % of control, suggesting additional effect in cortical nephron segments. Swelling of the kidney during diuresis may account for a reduction in metabolic rate per unit tissue volume of about 10 % of control. Scand J Clin Lab Invest Downloaded from informahealthcare.com by Flinders University of South Australia on 01/05/15 For personal use only. Scand J Clin Lab Invest Downloaded from informahealthcare.com by Flinders University of South Australia on 01/05/15 For personal use only. Scand J Clin Lab Invest Downloaded from informahealthcare.com by Flinders University of South Australia on 01/05/15 For personal use only.