Diurnal cardiovascular patterns in spontaneously hypertensive and Wistar-Kyoto rats.

Abstract

This study was designed to determine whether diurnal patterns of blood pressure, heart rate, or locomotor activity differed among two substrains of Wistar-Kyoto rats, derived originally from Charles River or Taconic Farms stock, or the spontaneously hypertensive rat Cardiovascular parameters were continuously monitored over 24 hours. Resting systolic and diastolic blood pressure values were statistically different among the three groups both during the lights-on (rest) and lights-off (active) phases of the cycle with blood pressure of spontaneously hypertensive rats greater than that of Wistar-Kyoto rats from Taconic Farms, which was greater than that of Wistar-Kyoto rats from Charles River. The largest difference in arterial pressure between Wistar-Kyoto/Taconic Farms and Wistar-Kyoto/Charles River was during the lights-on period. Heart rates of all rats decreased during the lights-on period; Wistar-Kyoto/ Charles River had the largest decrease ( -7 0 ± 5 beats/min), Wistar-Kyoto/Taconic Farms had the least (-17±2 beats/min), and in spontaneously hypertensive rats the decrease was intermediate (-29±3 beats/min). The pronounced diurnal variation in pressure and heart rate exhibited by Wistar-Kyoto/Charles River was not present in either Wistar-Kyoto/Taconic Farms or spontaneously hypertensive rats. Blood pressure magnitude correlated with locomotor activity during both periods, although all groups showed minimal activity during the rest period. Observed differences between Wistar-Kyoto/Charles River and Wistar-Kyoto/Taconic Farms were not due to a lack of or an abnormality in baroreceptor reflex function. Because most investigations that use these rat strains are performed during the lights-on phase of the diurnal cycle, the results demonstrate the need for a careful analysis of individual experimental protocols as well as the determination of the appropriate control for the spontaneously hypertensive rat (Hypertension 1990;16:422-428) T he suitability of the Wistar-Kyoto (WKY) inbred rat strain as the appropriate control for the spontaneously hypertensive rat (SHR) has been questioned by several groups within the past 2 years. Our concerns were raised in the early 1980s when we noted differences between WKY rats purchased from different vendors.After completion of a period of inbreeding by the National Institutes of Health (NIH) (20 generations of brother-sister mating), distribution of Wistarderived SHR obtained initially from Okamoto and Aoki 1 commenced in 1969. 2 The SHR strain has since achieved wide acceptance as an experimental model for essential hypertension. -4 For a control rat strain

Evaluation of the Long-Lasting Antihypertensive Action of 7-O-Ethylfangchinoline

“…Differently from hu man subjects, it has been reported that SHRs also reveal diurnal patterns, like normotensive rats do (22). The present results ascertained that circadian rhythms of blood pressure, HR, double product and ACT of SHRs were dependent on the dark/light cycle.…”

Chronobiological Aspects of the Heart Rhythm Disorders at the Change of Pulmonary Ventilation in Rat Model

“…Many experimental and clinical studies have demonstrated that cardiovascular functions show a marked circadian rhythmicity (Smith et al, 1987;Henry et al, 1990). Circadian fluctuations occur both in blood pressure and heart rate, but also in the ocurrence of ventricular dysrhythmias, the onset of cardiovascular symptoms, and the manifestations of cardiovascular diseases.…”

A new inbred Wistar-Kyoto rat substrain exhibiting apparent salt sensitivity and borderline hypertension

“…As a result, animals were distributed to commercial suppliers as early as the 10th generation of inbreeding (13). Furthermore, subsequent breeding was not standardized with some suppliers (including Charles River Laboratories) maintaining brother-sister matings (10) to sustain the founder stock, whereas others (including Taconic Farms) used a random breeding (outbred) protocol (26).Studies from several laboratories, including our own, compared WKY rats from Charles River Laboratories (WKY/cr; Wilmington, MA) and Taconic Farms (WKY/ tf; Germantown, NY) and reported pronounced trait differences (9,13,14,24). Our own laboratory (8), as early as 1984, noted differences in 1) consummatory behaviors including an enhanced salt preference in WKY/tf, 2) age-weight relationships, and 3) cardiovascular traits between these WKY substrains.…”

“…Studies from several laboratories, including our own, compared WKY rats from Charles River Laboratories (WKY/cr; Wilmington, MA) and Taconic Farms (WKY/ tf; Germantown, NY) and reported pronounced trait differences (9,13,14,24). Our own laboratory (8), as early as 1984, noted differences in 1) consummatory behaviors including an enhanced salt preference in WKY/tf, 2) age-weight relationships, and 3) cardiovascular traits between these WKY substrains.…”

“…Our own laboratory (8), as early as 1984, noted differences in 1) consummatory behaviors including an enhanced salt preference in WKY/tf, 2) age-weight relationships, and 3) cardiovascular traits between these WKY substrains. Furthermore, we reported distinct differences in resting systolic (SP) and diastolic (DP) arterial pressures and circadian variations among inbred WKY/cr, outbred WKY/tf, and inbred SHR/cr rats (9). Our colonies were begun in the early 1980s from breeder stock obtained from both Charles River Laboratories and Taconic Farms.…”