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B Tamaoki

Publications and source records attributed to B Tamaoki.

97 records · Page 6Linked to original sources
PubMedDate not supplied

A rapid measurement of delta 5-3 beta-hydroxysteroid dehydrogenase activity coupled with delta 4-delta 5 isomerase by a high pressure liquid chromatography.

By a high pressure liquid chromatography, progesterone (lambda max = 240 nm, epsilon 240 = 17,000) was separable from the other delta 4-3-oxosteroids. Relationship between the amount of progesterone and the area of the peak corresponding to progesterone was established as linear at least between 0-2.0 g. Progesterone is formed from pregnenolone by delta 5-3 beta-hydroxysteroid dehydrogenase coupled with delta r-delta 5 isomerase. Because pregnenolone is devoid of absorption oat 240 nm, the enzyme activity was measurable by the high pressure liquid chromatography from the amount of progesterone produced from pregnenolone in vitro in the presence of nicotinamide adenine dinucleotide. As an example of its application, the dehydrogenase activities in the ovaries of the immature rats treated with gonadotropins were measured by the above method. The estimates obtained by this method were agreeable with those by thin layer chromatography, employing radioactive pregnenolone as the substrate.

3-Hydroxysteroid Dehydrogenases↗
PubMedDate not supplied

In vitro decrease of lyase activity in rat ovarian cells during incubation: effect of hCG.

From PMSG-pretreated immature rats, dispersed ovarian cells were prepared with collagenase and DNase and incubated at 37 degrees C in McCoy's 5a medium under 95% air-5% CO2 atmosphere for 4 h. The activities of C17-C20 lyase measured in the 10,000 x g supernatant fluid of the cell homogenates decreased spontaneously with the lapse of time of the incubation. N,N'-Diphenyl-p-phenylenediamine (DPPD, an antioxidant) and actinomycin D inhibited the decrease most effectively. Cycloheximide was also an effective protector. Accordingly, the spontaneous decrease of the lyase activity was caused partly by an oxygen radical-mediated process and partly by a mechanism involving de novo synthesis of RNA and protein. Addition of hCG to the cells further decreased the lyase activity to about half of the control group at 4 h. DPPD itself did not affect the hCG-induced decrease of the lyase activity. However, actinomycin D and cycloheximide prevented the effect of hCG. These results indicate that de novo synthesis of RNA and protein is involved in the latter mechanism, while oxygen radical is not concerned in this process. The decrease of the enzyme activity by hCG during incubation is in agreement with the in vivo effect of hCG upon the lyase activity. On the contrary, at the end of incubation the activity of delta 5-3 beta-hydroxysteroid dehydrogenase (coupled with delta 5-delta 4 isomerase) was more than 89% of that before incubation, and the change of the enzyme activity according to the various treatments was less than 16%.

Animals↗