Metabolism of round spermatids: evidence that lactate is preferred substrate.

M. Nakamura, S. Okinaga, K. Arai

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Abstract

Glucose was utilized at a rate of 17.9 +/- 1.0 nmol X 10(6) cells-1 X h-1, with 5.2 and 9.5% accumulated as glucose and fructose 1,6-diphosphate, respectively, 79.6% transformed into lactate, 2% oxidized by the trichloroacetic acid cycle, and little metabolized by the pentose cycle. Glucose utilization increased and reached a maximum at 1 mM glucose. The ATP level was maintained by approximately 0.8 mM lactate, but not by glucose or pyruvate. Glucose decreased the ATP level to a value lower than the control level due partly to the fructose 6-phosphate-fructose 1,6-diphosphate futile cycle. In the presence of lactate (0.01-20 mM), pyruvate production was increased, but the intracellular level of pyruvate (0.2-0.3 mM) remained unchanged. Lactate dehydrogenase (LDH) activity was increased, at a maximum rate, by 0.1-0.2 mM pyruvate but was inhibited beyond 0.3 mM (Ki = 2.5 mM). The Km values of LDH for pyruvate and lactate were 24.4 +/- 4.2 microM and 2.36 +/- 0.14 mM, respectively. The importance of LDH in glucose and lactate metabolism by spermatids was described. These observations further support the hypothesis that lactate is the preferred substrate for spermatid metabolism.

Original languageEnglish
JournalThe American journal of physiology
Volume247
Issue number2 Pt 1
Publication statusPublished - 1984 Aug
Externally publishedYes

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ASJC Scopus subject areas

  • Medicine(all)

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