Metabolism of round spermatids: Evidence that lactate is preferred substrate

M. Nakamura, S. Okinaga, K. Arai

Research output: Contribution to journalArticle

Abstract

Glucose was utilized at a rate of 17.9 ± 1.0 nmol · 106 cells-1 · 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-disphosphate futile cycle. In the presence of latate (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 [K(i) = 2.5 mM]. The K(m) values of LDH for pyruvate and lactate were 24.4 ± 4.2 μM 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
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume10
Issue number2
Publication statusPublished - 1984
Externally publishedYes

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ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology
  • Physiology

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