Oxygen Consumption in the Spontaneously Hypertensive Rat

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Abstract
O2 utilization was elevated in SH [spontaneously hypertensive] rats as compared to control animals; the difference was statistically significant at ambient temperatures (T2) above 25.degree. C. Corresponding elevations in rectal temperature were noted. The enhanced metabolic response was related to the relative inability of the hypertensive rat to prevent rectal temperature elevation during heart stress. Whether the increase in O2 uptake was a causal factor or resulted from body temperature elevation due to defective heat loss by the SH rat was unclear. Propranolol induced a significant reduction in O2 usage of both SH and WKY rat groups at Ta 30.degree. C but not at 21.degree. indicating an adrenergic influence on metabolic rate during acute heat stress which was absent during cooler exposures. Serum T4 [thyroxine] levels of SH were not significantly different from control values whereas T3 [triiodothyronine] levels were elevated (26%) indicating normal or slightly increased thyroid activity. In comparison, TSH [thyroid stimulating hormone] levels were elevated 4-fold indicating a markedly abnormal thyroid response to the hormone.

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