HYPERTENSION, AGING, AND MYOCARDIAL SYNTHESIS OF HEAT-SHOCK PROTEIN-72

We determined the temperature-induced synthesis of the 72-kD heat-shoc k protein (hsp72) in hearts of normotensive and spontaneously hyperten sive rats (SHR) subjected to whole-body hyperthermia (42.0+/-0.5 degre es C for 15 minutes). The animals were studied at three different ages : young (2 months), adult (6 months), and old (18 months). The hsp72 w as determined by Western blot analysis using a monoclonal antibody. Th e results were calculated densitometrically as a percentage of a comme rcial standard. Young SHR responded to hyperthermic stress with increa sed synthesis of hsp72 compared with age-matched normotensive rats (29 8.8+/-70.0% versus 88.3+/-25.5%). This trend was maintained in adult r ats (118.1+/-31.0% versus 54.8+/-21.3%) but not in old rats (65.3+/-29 .4% versus 43.6+/-15.1%). Aging caused a reduction of hsp72 expression in response to hyperthermic stress in both SHR (4.6-fold) and normote nsive rats (twofold). These data show that hearts of young and adult S HR respond to heat shock with enhanced synthesis of hsp72. This abnorm al response, attenuated by aging, is independent of the presence and d egree of hypertension or hypertrophy and is potentially linked to the genetic determination of the-disease.