GENDER AND DIETARY NACL IN SPONTANEOUSLY HYPERTENSIVE AND WISTAR-KYOTO RATS

We recently reported that high dietary NaCl exposure significantly inc reases both daytime and nighttime mean arterial pressure in male spont aneously hypertensive rats (SHR) but only nighttime values in male nor motensive Wistar-Kyoto rats (WKY). In the present study we used a tele metry monitoring system to evaluate the effects of high dietary NaCl e xposure on diurnal variation of mean arterial pressure and heart rate in male and female SHR and WKY. After implantation of a radio-frequenc y transducer, rats were fed either high (8%) or basal (1%) NaCl diets for 2 weeks. High dietary NaCl ingestion significantly increased both daytime and nighttime mean arterial pressure in male SHR compared with males receiving a basal NaCl diet, resulting in greater 24-hour value s (163+/-1 versus 154+/-1 mm Hg, high versus basal NaCl diet; P<.05). High dietary NaCl ingestion significantly increased only nighttime blo od pressure in male WKY, with no significant effect on 24-hour mean ar terial pressure (102+/-2 versus 101+/-3 mm Hg, high versus basal). Hig h dietary NaCl exposure did not affect daytime or nighttime mean arter ial pressure in female SHR (24-hour mean arterial pressure, 144+/-2 ve rsus 141+/-2 mm Hg, high versus basal NaCl diet). Twenty-four-hour mea n arterial pressure tended to be lower in female WKY receiving a high NaCl diet than females ingesting a basal diet (101+/-3 versus 106+/-1 mm Hg), but the difference was not significant. These results indicate a sexually dimorphic response to dietary NaCl ingestion, with males o f both strains manifesting some degree of NaCl sensitivity, whereas fe males are NaCl resistant.