C-type natriuretic-peptide-potentiated relaxation response of gastric smooth muscle in streptozotocin-induced diabetic rats.
OBJECTIVE
To study the sensitivity of gastric smooth muscle to C-type natriuretic peptide (CNP) in streptozotocin (STZ)-induced diabetic rats.


METHODS
The spontaneous contraction of a gastric smooth muscle strip was recorded by using physiological methods in rats. The expressions of CNP and natriuretic peptide receptor-B (NPR-B) in gastric tissue were examined by using immunohistochemistry techniques in the diabetic rat.


RESULTS
At 4 wk after injection of STZ and vehicle, the frequency of spontaneous contraction of gastric smooth muscle was significantly reduced in diabetic rats, and the frequency was decreased from 3.10 +/- 0.14 cycle/min in controls to 2.23 +/- 0.13 cycle/min (n = 8, P < 0.01). However, the amplitude of spontaneous contraction was not significant different from the normal rat. CNP significantly inhibited spontaneous contraction of gastric smooth muscle in normal and diabetic rats, but the inhibitory effect was significantly potentiated in the diabetic rats. The amplitudes of spontaneous contraction were suppressed by 75.15% +/- 0.71% and 58.92% +/- 1.32% while the frequencies were decreased by 53.33% +/- 2.03% and 26.95% +/- 2.82% in diabetic and normal rats, respectively (n = 8, P < 0.01). The expression of CNP in gastric tissue was not changed in diabetic rats, however the expression of NPR-B was significantly increased in diabetic rats, and the staining indexes of NPR-B were 30.67 +/- 1.59 and 17.63 +/- 1.49 in diabetic and normal rat, respectively (n = 8, P < 0.01).


CONCLUSIONS
The results suggest that CNP induced an inhibitory effect on spontaneous contraction of gastric smooth muscle, potentiated in diabetic rat via up-regulation of the natriuretic peptides-NPR-B-particulate guanylyl cyclase-cyclic GMP signal pathway.
Department of Physiology, Yanbian University School of Medicine, 1829 Juzi Rd, Yanji 133000, Jilin Province, China.
Ying-Lan
YL
Cai
Dong-Yuan
DY
Xu
Xiang-Lan
XL
Li
Zhang-Xun
ZX
Qiu
Zheng
Z
Jin
Wen-Xie
WX
Xu
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D018589:Gastroparesis / Q000378:metabolism; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D009126:Muscle Relaxation / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D020098:Natriuretic Peptide, C-Type / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017461:Receptors, Atrial Natriuretic Factor / Q000378:metabolism; D013270:Stomach / Q000033:anatomy & histology*; D000099242:Atrial Natriuretic Factor Receptor B
D001786:Blood Glucose; D020098:Natriuretic Peptide, C-Type; D017461:Receptors, Atrial Natriuretic Factor; D000099242:Atrial Natriuretic Factor Receptor B