Using a novel radio-respirometer, the relative activity of the pentose phosphate pathway has been determined at various stages of development of the chick embryo, by comparing the recovery of Cl402 from glucose labeled in position one (G-1) to that from glucose labeled in position six (G-6). Respirometry was performed on the intact embryo in ovo using concentrations of glucose within the range found in normal embryonic body fluids. Significantly greater recovery of C'*OZ from G-1 relative to that from G-6 was obtained at 68-72 hours and again at 6-8 days. These periods correspond in temporal position with previously reported maxima in glucose-6-phosphate dehydrogenase activity in the brain of the developing chick embryo and are considered to support the interpretation that patterns of the enzyme activity, determined on homogenates in vitro, reflect patterns of activity of the pentose phosphate pathway in ovo.
- Supported by grants GB-1153 from the National Science Foundatlon and GM 11238 from the Natzonal Institutes of Health, USPHS.
2 Abbreyiations used: NADPH, reduced nicotinamide aderune dinucleotide phosphate; G-1, glucos!? labeled with Cla in posiuon 1; G-6, glucose labeled wlth C14 in position 6; GGPDH, glucose-6-phosphate dehydrogenase; G1/G-6 ratio is defined as the ratio of recovew of ?arbon-1 of glucose to that of carbon-6, in the respiratory COz.