Relationship between vascular adrenergic receptors and prostaglandin biosyntheses in canine diabetic coronary arteries

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Abstract
Before the onset of histologically detectable alterations of diabetic arteries, a considerable decrease of vasodilation ability develops. The role of an altered prostaglandin biosynthesis in this phenomenon was investigated in connection to the altered vascular adrenergic mechanisms. The effect of phenylephrine on prostacyclin production of isolated coronary arterial rings (100 μmol/l) as well as on conductivity of the coronary arterial bed (7.5-15-30-60 pmol·kg−1·min−1) were compared in 12 metabolically healthy and 12 alloxan-diabetic (560 μmol/kg) dogs. Furthermore, the effect of phentolamine (5 μmol/l) on the prostacyclin and thromboxane productions of the isolated vessels (coronary, femoral and basilar arteries) was investigated by radioimmunoassay. Although the basal prostacyclin amounts synthesized by healthy and diabetic coronary vessels were not different (5.1±1.6 and 4.9±1.4pg/mg vessel/30 min), similarly to femoral and basilar arteries, the diabetic arterial rings produced significantly (ppppp<0.05) decrease in the coronary conductivity in diabetic than in control groups. These results refer to the supposition that altered adrenergic mechanisms are involved in the imbalamce of the vasoactive prostaglandins contributing to the high incidence of ischaemic heart disease in diabetes mellitus.