Bunji Hagihara

Measurement of Hemoperfusion and Oxygen Sufficiency in Gastric Mucosa In Vivo: Evidence of Mucosal Hypoxia as the Cause of Hemorrhagic Shock-Induced Gastric Mucosal Lesion in Rats

Reflectance spectrophotometry was applied to the rat gastric mucosa in vivo to determine the hemodynamics as well as the intracellular oxygen metabolism. In the spectra obtained, the hemoglobin absorbances gave information as to mucosal blood volume and average oxy- and deoxyhemoglobin equilibrium, while the oxidation-reduction levels of the respiratory chain cytochromes determined the tissue oxygen saturation. In resting, air-breathing rats, the reflectance spectra showed a predominant oxyhemoglobin absorbance with almost fully oxidized cytochrome absorbances, suggesting a balanced oxygen supply and utilization. The mucosal blood volume was greater in the corpus region than in the antral region. The hemorrhagic shock caused a significant reduction of hemoglobin absorbances and induced an almost full reduction of the respiratory chain cytochromes in the corpus mucosa, indicating a severe reduction of blood supply resulting in severe hypoxia in the corpus mucosal cells. In contrast, the reflectance spectra of antral mucosa showed only a slight fall in the hemoglobin absorbance with no appreciable change of redox levels of the respiratory chain cytochromes. The mucosal hemorrhage and lesion appeared only in the corpus region, where the reduced cytochrome absorbances had been manifest. Thus, the present paper presents direct evidence supporting the concept that disturbed energy metabolism in the gastric mucosa is the cause of acute mucosal lesion during hemorrhagic shock. Further, this study represents a noninvasive methodology for measuring the intramucosal oxygen insufficiency that would precede the formation of the gastric mucosal lesion in the face of hemorrhagic shock.

pH-dependent interaction of microsomal cytochrome P-450 with substrates. I. Effect of pH upon the interaction of exogenous substrates with membrane-bound cytochrome P-450

The interaction of microsomal membrane-bound cytochrome P-450 with substrates was studied spectrophotometrically at various pH-values. The binding of type I compounds, hexobarbital and androstanedione, with cytochrome P-450, as determined by the magnitude of the type I spectral change of microsomes, was markedly enhanced at alkaline pH compared to that at acid pH. The pH-dependent spectral change could be reversed by changing the pH. The maximum absorption change (delta Amax) increased with increasing the pH, while the spectral dissociation constant (Ks) decreased. A similar pH-dependent binding reaction was also observed using a non-dissociative type I compound, cyclohexane. On the contrary, the absorbance magnitude between peak and trough in the aniline- or alcohol-induced difference spectrum of microsomes was enhanced by decreasing the pH, indicating easy complex formation of type II and reverse type I compounds with cytochrome P-450 in the acid rather than the alkaline region.

8 Type b Cytochromes

Publisher Summary Type b cytochromes are electron-carrying proteins, which contain protoheme IX as the prosthetic group. The position of α band of their absorption spectra in the ferrous state ranges from 554 to 566 nm. By the pyridine treatment they give the pyridine-protohemochrome with its α band at 556 nm. They are widespread in animals, plants, and various microorganisms. Many type b cytochromes associated with the classic cytochrome oxidase show α peak at 561-563 nm, and they are usually designated as cytochrome b. The name cytochrome b1 was originally used for the pigments with a peak at 557-560 nm, but it is now generally applied to the cytochrome in the nitrate reductase system. Various other type b cytochromes are found in invertebrates, protozoa, bacteria, fungi, algae, and higher plants. The presence of different cytochrome b components in mitochondria1 respiratory chain and their direct role in energy conservation have been postulated for many years. These postulations were based on anomalous kinetic and spectrophotometric behavior of the b cytochromes in intact mitochondria and in phosphorylating submitochondrial particles.

ANALYSIS OF MITOCHONDRIAL AND MICROSOMAL CYTOCHROMES IN HUMAN LIVER BIOPSY

Publisher Summary This chapter presents the analysis of mitochondrial and microsomal cytochromes in human liver biopsy. It discusses a new method for measuring simultaneously the contents of the cytochromes aa3, P-450 and b5 in very small sample obtained by needle biopsy. The result obtained shows no significant change of cytochrome aa3 content in drinkers livers, while a significant increase in the liver cytochrome P-450 content was observed with concomitant change of the ratio of P-450/b5 contents by chronic alcohol intake. Studies on mitochondrial and microsomal cytochromes in human livers have been carried out in relation to ethanol metabolism. To determine the cytochrome content in small biopsy samples, a micromethod was developed, in which different CO reassociation behavior among cytochromes aa3, P-450, and hemoglobin after photolysis of the CO-treated sample at low temperature was utilized.