Identification of the product of heme degradation catalyzed by the heme oxygenase system as biliverdin IX alpha by reversed-phase high-performance liquid chromatography

Biliverdins formed from heme by a microsomal preparation and a reconstituted heme oxygenase system were each converted to their dimethyl esters and analyzed for isomeric composition by reversed-phase high-performance liquid chromatography, using a column of mu Bondapak C18 (Waters Associates); on this column, the dimethyl esters of four biliverdin IX isomers, that is IX alpha, IX beta, IX gamma, and IX delta, have been shown to be eluted separately in the order IX alpha, IX beta, IX delta, and IX gamma, when developed with methanol/water. The analysis indicated that the enzymatically formed biliverdins were exclusively IX alpha; the elution profile exhibited no other significant elution peak due to other biliverdin isomers. It was concluded that the heme oxygenase system cleaves the heme ring specifically at the alpha-methene bridge to yield biliverdin IX alpha.

Photo-reversal by monochromatic light of the carbon monoxide-inhibited heme degradation catalyzed by the reconstituted heme oxygenase system

Photo-reversal of the carbon monoxide inhibition of heme oxygenase reaction by monochromatic light was investigated. Heme degradation in either the microsomal or the reconstituted heme oxygenase system was inhibited by CO. In both systems the extents of Co inhibition were dependent on the CO/O2 ratio and were nearly equal at a given CO/O2 ratio. In the reconstituted heme oxygenase reaction using a highly purified heme oxygenase preparation the relationship between the intensity of light and the degree of reversal of the CO inhibition of heme degradation as expressed in terms of delta K/Kd was not linear, but the tentatively obtained photochemical action spectrum exhibited the peaks of reversal at about 420, 540, 570, and 640 nm and suggested the occurrence of at least two steps of CO inhibition in the overall sequence of heme degradation. One could be ascribed to protoheme and the other was supposed to be the 688 nm compound which is an intermediate locating between hydroxyheme and the biliverdin-iron complex in the sequence of heme degradation.

Degradation of mesoheme and hydroxymesoheme catalyzed by the heme oxygenase system: involvement of hydroxyheme in the sequence of heme catabolism

Mesoheme bound to heme oxygenase protein was easily degraded to mesobiliverdin by incubation with NADPH-cytochrome c reductase and NADPH. The features of mesoheme degradation were very similar to those of protoheme degradation catalyzed by the heme oxygenase system; an intermediate compound having its absorption maximum at 660 nm appeared in the couse of mesoheme degradation and this compound is presumably equivalent to the 688 nm compound which appears in the course of protoheme degradation. Hydroxymesoheme was chemically prepared and a complex of hydroxymesoheme and heme oxygenase was prepared. The complex was fairly stable in air, but when the complex was incubated with the NADPH-cytochrome c reductase system, the hydroxymesoheme bound to heme oxygenase was readily converted to mesobiliverdin through the 660 nm compound as an intermediate. It is evident that hydroxyheme is a real intermediate of heme degradation in the heme oxygenase reaction and that the 688 nm compound (or the 660 nm compound in the mesoheme system) is located between hydroxyheme and the biliverdin-iron chelate. The ferrous state of heme-iron may also be necessary for the onset of further oxidation of hydroxyheme.

Mechanism of the excitatory action of motilin on isolated rabbit intestine

Synthetic motilin caused a dose-dependent contraction on isolated rabbit intestinal segments, including the duodenum, ileum, and rectum. The contraction of duodenum was significantly greater than that in the ileum or rectum. In the duodenum, motilin was approximately 100 times as potent as acetylcholine on molar basis. The motilin-induced contractions were not influenced by atropine, chlorpheniramine, cimetidine, phentolamine, propranolol, cinanserin, 1-sar-8-ala-angiotensin II, or aspirin. Motilin did not affect the contraction induced by transmural electrical stimulation or acetylcholine. The response to motilin was unaffected by acetylcholine. Removal of Ca++ from bathing media or verapamil suppressed the motilin-induced contractions to a significantly greater extent than the contractions induced by acetylcholine. Thus, it may be concluded that motilin produces intestinal contractions by acting directly on smooth muscles, but not by acting on pharmacologically known drug receptors nor by releasing neurotransmitters such as endogenous acetylcholine. Motilin does not appear to modify autonomic nerve functions.

Radon Anomaly: A Possible Precursor of the 1978 Izu-Oshima-kinkai Earthquake

Precursory changes in the radon concentration of groundwater were observed prior to the Izu-Oshima-kinkai earthquake (magnitude 7.0) 14 January 1978. The distance from the epicenter to a continuous radon-monitoring station at Nakaizu was about 25 kilometers. A sudden drop and a subsequent increase in the radon concentration recorded on 9 January 1978 were significant. The size of the spike-like change was about 15 percent. After the earthquake, a remarkable increase in the radon concentration occurred.