ABSTRACT
Exercise is associated with an increase in plasma renin activity (PRA). The purpose of this study was to determine the role of the prostaglandin (PG) and adrenergic pathways in the renin release with exercise in the dog. One group of animals (n = 4) was exercised under control untreated and indomethacin- and meclofenamate- (2 mg/kg) treated conditions. A 155% increase in PRA was not influenced by PG inhibition. In a second group (n = 7) PRA was 1.22 +/- 0.32, 3.29 +/- 1.59, 6.28 +/- 2.85, and 5.30 +/- 2.00 ng ANG I X ml-1 X h-1 at rest and during light, moderate, and heavy exercise, respectively. Guanethidine treatment (15 mg/kg) decreased mean PRA by 41, 50, 70, and 73% at rest and during the three levels of exercise, respectively. In a third group (n = 5) control exercise runs were repeated after metoprolol treatment. Selective beta 1-blockade completely abolished the increment in PRA observed with exercise. These data demonstrate that the elevation of PRA during exercise in the dog is mediated by increased sympathetic nerve activity involving beta 1-receptors and that it is not dependent on alterations in PG synthesis.
Subject(s)
Physical Exertion , Renin/metabolism , Animals , Blood Pressure/drug effects , Dogs , Female , Guanethidine/pharmacology , Heart Rate/drug effects , Indomethacin/pharmacology , Meclofenamic Acid/pharmacology , Prostaglandin Antagonists/pharmacology , Renin/bloodABSTRACT
Oxygen consumption was measured in Yucatan miniature swine during various intensities of treadmill exercise. Nine animals were evaluated at rest and at various treadmill velocities ranging from 2.5-4.5 mph. Oxygen consumption was linearly related to treadmill speed during sub-maximal exercise work loads (r = 0.92, P less than 0.01). Maximal oxygen consumption was also determined in two groups of animals. In one group (N = 6) the highest attainable oxygen consumption was 24.0 +/- 1.31 ml . min-1 . kg-1. In the second group (N = 9) an electric prod was utilized to encourage the animals to run. Their maximal oxygen consumptions ranged from 33.9-51.1 ml . min-1 . kg-1 with a mean of 41.7 +/- 1.8 ml . min-1 . kg-1. These data indicated that Yucatan swine have a relatively low aerobic capacity compared to the rat or dog, but their oxygen consumptions are similar to that observed in untrained man.
Subject(s)
Oxygen Consumption , Physical Exertion , Swine/physiology , Animals , MaleABSTRACT
The purpose of this study was to determine if exercise was associated with alterations in renal cortical sialic acid content or glomerular capillary anionic character. These factors have been shown to be important, insofar as they contribute to an electrostatic barrier which prevents the filtration of negatively charged macromolecules. In unilaterally nephrectomized dogs (n=7), exercised kidneys tended to have increased amounts of sialic acids and a decrease in glomerular anionic character, as evaluated by the intensity of colloidal iron staining, however, nephrectomy alone also caused similar changes. Additional experiments were conducted using rat litter mates assigned to control or treadmill-exercise groups. Exercised animals were run for 60-80 min. Renal cortical sialic acids were 2.74 +/- 0.07 mumol/g for controls (n=12) and 3.03 + 0.09 mumol/g for the exercised animals (n=10) (P less than 0.05). Colloidal iron staining, rated on a 0-3 scale (0=no uptake, 3=maximum staining) was 2.5 +/- 0.1 and 1.3 +/- 0.3 for the controls and exercised animals, respectively (P less than 0.05). Colloidal iron staining remained below control levels for 24 h post-exercise. These data suggest that exercise increases glomerular sialic acid content and decreases colloidal iron staining. This latter effect may decrease the glomerular capillary electrostatic barrier and thereby may be an important factor in causing exercise proteinuria.
