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SUMMARY. The objectives of this study were to measure action potential parameters in enzymedissociated, adult rat ventricular myocytes stimulated at 1 Hz, to compare these measurements with those obtained from intact ventricular tissue, and to determine myocyte and tissue responses at stimulus frequencies between 0.1 and 5 Hz. Action potentials were characterized in terms of amplitude, overshoot, resting potential, duration at 25% and 75% repolarization (APD25, APD75), and V max . Based on statistical differences in APD25 and APD75, myocyte action potentials were classified as type 1 (3.1 ± 1.0 and 21.5 ± 3.6 msec), type II (7.4 ± 1.1 and 38.2 ± 6.7 msec), or type III (14.5 ± 1.9 and 46.0 ± 4.1 msec). Action potentials corresponding to type I were found in right ventricular endocardium and right papillary muscles, and those corresponding to types II and III in the left ventricular endocardium [apex, middle (II); base (III)] and left papillary muscles (II). Myocytes and papillary muscles responded to increases in driving rate with nearly identical lengthening of APD25 and shortening of APD 75 . The one exception was at 5 Hz where a lengthening of the APD75 occurred in some myocytes. We conclude that action potential configuration in rat ventricle is heterogeneous, and that this is reflected by the different types of action potentials in isolated myocytes. It is likely that the magnitude of a transient outward current is a determinant of action potential configuration, and that slow reactivation of this current is a significant factor underlying the stimulus frequency response. (Ore Res 52: 280-290, 1983)

ABSTRACT. The systolic, mean and diastolic pressures as well as the heart rate were mesured using the oscillometric method, on a total of 104 cats (60 cats in the normal group, and 44 in the renal disease group) which were brought into Azabu University Animal Hospital. The blood pressure in the normal group was systolic: 115.4 ± 10.1 mmHg, mean: 96.2 ± 12.2 mmHg, and diastolic: 73.7 ± 10.7 mmHg. Although no difference in heart rate, the renal disease group showed significantly (p<0.05) higher values for systolic, mean, and diastolic pressure when compared with the normal group. Moreover, when plasma renin activity, angiotensin I and II, and aldosterone concentrations were measured in other cats (11 normal and seven with chronic renal failure), all cats with chronic renal failure showed significantly (p<0.05) higher values than the normal group. It is, therefore, indicated that hypertension due to stimulating renin-angiotensin-aldosterone system may have manifested in cats with renal dysfunction. -KEY WORDS: blood pressure, feline, hypertension, renin-angiotensinaldosterone system. J. Vet. Med. Sci. 60 (7): [805][806][807][808] 1998 vomitus and anemia), and high concentrations (range: 2.1-13.8 mg/dl; mean: 3.9 ± 3.0 mg/dl) of serum creatinine, were classified as the renal disease group. A sphygmomanometer (USM-700GTM : Ueda Electronic Works, Ltd.), oscillometric method, was used to measure the systolic, mean, diastolic pressures and the heart rate in both groups. The blood pressure measurement sites were either the forelimb or the tail, and a measuring cuff was selected based on the size of approximately 40% circumference of the measuring site. In order to avoid stress to the patients as much as possible, blood pressure was measured in an isolated room apart from the regular consulting room. Moreover, the blood pressure was measured a total of five times at one minute intervals with the owner's presence. The results obtained under the physical movements of the patient were deleted from the values as artifacts.The effects of the number of measurements on the blood pressure and heart rate were firstly examined in the normal group. To examine the effects of measuring sites on the blood pressure, the blood pressure of both the forelimb and the tail was compared using a total of 24 cats selected randomly from the normal group. The effects of both gender and age on blood pressure were examined in the normal group. Thereafter, these values obtained from both the normal and the renal disease groups were analyzed.The plasma renin activity, angiotension I and II, and aldosterone concentrations were measured to by radioimmunoassay compare 11 normal to seven cases with chronic renal dysfunction.The statistical analysis on the number of measurements were conducted, first using the Friedman method, followed by the Wilcoxon method. The Speaman raking correlation Hypertension has been recognized as a risk factor in human patients with cerebral hemorrhage, heart and renal diseases, therefore diagnosis of hypertension is carrie...

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