Exaggerated Stress Responses of a Chromosome-1 Congenic Strain Derived from Shrsp/Izm and Wky/Izm
Background: QTL mapping studies showed that the rat chromosome 1 includes a gene responsible for hypertension in SHR. To understand roles of this putative hypertension gene on the cardiovascular physiology, we studied stress responses of a congenic strain with the chromosome-1 blood pressure (BP) QTL transferred from SHRSP/Izm. Methods: The region between D1Wox29 and D1Rat112 (∼60cM) was introgressed from SHRSP/Izm to WKY/Izm by repeated backcrossing. The established congenic strain (CONG) covered a 100:1 support interval for the BP QTL found in the previous study (Am J Hypert 1999;12:1098). After telemetry probes were implanted, age-matched male CONG and WKY (5-6 month old) were used in the following experiments; 1) Restraint stress: rats were put in small tubes for 1h at room temperature and BP was monitored with radiotelemetry. 2) Cold stress: rats were kept at 4 C for 2h and BP was monitored using telemetry. Results: Without the stresses, BP measured with telemetry was not different between WKY and CONG (Table) although tail-cuff measurement gave a significant difference in BP between the two strains (141±3.5 and 154±8.3mmHg for WKY and CONG, p<0.0001). During the exposure to the restraint stress, CONG showed greater BP increase than did WKY (Table). Similar exaggerated responses in CONG were observed during the cold stress as well. Conclusion: The hypertension gene in the chromosome-1 QTL region may modulate cardiovascular responses to the stresses probably through the sympathetic nervous system.