Increased monoamine oxidase activity and imidazoline binding sites in insulin-resistant adipocytes from obese Zucker rats

Figure 4 Oxidation of tyramine by membrane preparations from different tissues of obese and lean Zucker rats. Crude membranes prepared by centrifugation from adipocytes isolated from visceral white adipose tissue, or from the liver, brown adipose tissue, and soleus muscle, were incubated for 20 min at 37 °C with 0.5 mmol/L ¹⁴C-tyramine in phosphate buffer (200 mmol/L) without (total oxidation), with 1 mmol/L semicarbazide (monoamine oxidase, MAO), or with 1 mmol/L pargyline (semicarbazide-sensitive amine oxidase, SSAO). The minor oxidation remaining in the presence of both inhibitors (semicarbazide + pargyline), therefore non-SSAO and non-MAO, was subtracted in all cases. Mean ± SEM from four determinations for lean (open columns) and five for obese male rats (dark columns); ND: Non-detectable. Significantly different from lean at: ^aP < 0.05; ^bP < 0.01; ^cP < 0.001.