[Relaxation of vascular smooth muscle induced by formaldehyde (author's transl)]

Using spiral strips of male rabbit thoracic aortae, we examined the effect of formaldehyde (HCHO) on vascular smooth muscle. HCHO (6.6 X 10(-4)M) did not inhibit the tonic contraction induced by 25 mM K+, while inhibition was apparent with a pretreatment of HCHO in the same dose. HCHO markedly inhibited Ca2+-induced contraction in the preparation depolarized by excess K+ in Ca2+-free media, but did not inhibit 50 mM K+-induced contraction in the preparation exposed to Ca2+-free media (EGTA deleted). In addition, HCHO did not inhibit the contraction induced by 2.2 mM Ba2+ in the preparation exposed to Ca2+-free media (added EGTA). These results suggest that HCHO inhibits the transmembrane influx of Ca2+. The contraction induced by norepinephrine (NE) was also inhibited by HCHO. High performance liquid chromatography revealed that NE was rapidly inactivated by HCHO in Krebs-bicarbonate solution at 37 degrees C. This finding suggests that the inhibitory effect of HCHO on the contraction induced by NE is mainly due to inactivation of NE. Therefore, the relaxation of the vascular smooth muscle induced by HCHO is probably mainly related to both the inactivation of catecholamines and the inhibitory effect on transmembrane influx of Ca2+.