Cytochemical investigation of glucose-6-phosphate dehydrogenase activity in rat mammary tissue.

Glucose-6-phosphate dehydrogenase (G6PD) activity in epithelial cells from six normal, eight lactating and 21 DMBA tumour bearing rat mammary tissues was investigated using techniques of quantitative cytochemistry. G6PD promoted H+ production was quantified under atmospheres of N2 and O2 in frozen sections from rat mammary tissue in the presence and absence of a H+ acceptor (Total H+ and Type I H+). There was a considerable overlap between the three tissue types in values for Total H+ measured under N2 or O2. However, maximum H+ production in lactating and DMBA tumour tissue took longer to achieve in O2 than in N2 (16-20 min vs 6-8 min). In normal tissue maximum production of Total H+ was not achieved until 45-50 min and the rate of reaction was similar in N2 and in O2. Type I H+ measured in N2 did not vary significantly between DMBA tumours and lactating tissue but under O2 was only present in DMBA tumour, being undetectable in both normal and lactating tissue. The results demonstrate that despite the overlap in G6PD activities between the tissues tested, the techniques of quantitative cytochemistry can provide a functional assay differentiating between non-malignant and malignant breast tissue in the rat.