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EFFECTS OF HYDROXOCOBALAMIN AND HAEMOGLOBIN ON NO‐MEDIATED RELAXATIONS IN THE RAT ANOCOCCYGEUS MUSCLE
Author(s) -
Li C. G.,
Rand M. J.
Publication year - 1993
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1993.tb01645.x
Subject(s) - hydroxocobalamin , chemistry , sodium nitroprusside , stimulation , nitric oxide , medicine , endocrinology , muscle relaxation , biochemistry , cyanocobalamin , vitamin b12 , organic chemistry
SUMMARY 1. The effects of hydroxocobalamin (Vitamin B 12a ) on relaxations produced by nitric oxide (NO), some NO‐donating compounds and nitrergic nerve stimulation in isolated preparations of the rat anococcygeus muscle were compared with the effects of haemoglobin. 2. Hydroxocobalamin (30 μmol/L) significantly reduced relaxations induced by NO (0.1–3 μmol/L) and sodium nitroprusside (SNP; 0.01–0.3 μmol/L) but did not affect relaxations induced by glyceryl trinitrate (GTN; 0.01–1 μmol/L), S‐nitrosocysteine (0.1–0.3 μmol/L) or stimulation of nitrergic nerves. A higher concentration of hydroxocobalamin (100 μmol/L) slightly reduced nitrergic nerve stimulation‐induced relaxations. 3. Haemoglobin (10 μmol/L) blocked relaxation induced by NO and reduced relaxations induced by SNP, GTN, S‐nitrosocysteine and nitrergic nerve stimulation. 4. When nitrergic nerve stimulation‐induced relaxations had been partially reduced by the NO synthase inhibitor l‐NAME (5–10 μmol/L), hydroxocobalamin had only a weak and transient inhibitory effect. 5. Noradrenergic contractions induced by field stimulation were not affected by hydroxocobalamin (30 μmol/L), but were enhanced by haemoglobin (10 μmol/L). 6. The results suggest that the transmitter released from nitrergic nerves in anococcygeus muscles resembles NO‐releasing compounds such as S‐nitrosocysteine and GTN but not SNP or free NO.