AGE-DEPENDENT CHANGES IN PARTICULATE AND SOLUBLE GUANYLYL CYCLASE ACTIVITIES IN URINARY-TRACT SMOOTH-MUSCLE

Regional and age specific differences are observed in the sodium nitro prusside induced relaxation responses in the urinary tract. To clarify these differences, guanylyl cyclase activity is assayed in particulat e and soluble fractions from the ureter, bladder dome, and urethra of young (11-18 days), adult (90-100 days), and old adult (2-3 years) gui nea pigs. The rank order of soluble guanylyl cyclase activities is ure thra = ureter > bladder dome with the largest decreases with aging occ urring in the bladder. Atrial natriuretic factor(10(-7) M) increases p articulate guanylyl cyclase activity in the three tissues at all ages tested, with the activity being highest in the ureter. ATP (0.5 mM) ac tivates particulate guanylyl cyclase in the ureter, bladder and urethr a of old adult guinea pigs, and enhances atrial natriuretic factor ind uced activation of particulate guanylyl cyclase in all tissues and at all ages tested. The higher levels of soluble guanylyl cyclase activit y in the urethra and ureter compared to the bladder parallel sodium ni troprusside induced relaxation in these tissues.