https://www.news-medical.net/news/20...ar-system.aspx

Specifically, they focused on the connection between PKA and adenylyl cyclase (AC), an enzyme involved in cyclic AMP (cAMP) production. They found that AC5 facilitated cAMP and PKA activation, stimulating increase calcium channel activity and subsequent blood vessel vasoconstriction. Also, they discovered that AC5 was crucial for blood vessel vasoconstriction during diabetes.
This is fascinating. And yet another reason to keep one's blood glucose low even for non-diabetics. One of the many classes of drugs they offer people with hypertension are calcium channel blockers -- supposedly to prevent vasoconstriction and reduce blood pressure. I'm guessing that if one has chronically elevated blood glucose (as many diabetics on the "carb up and shoot up" plan do) then the increased calcium channel activity will override any effect of calcium channel blockers.

Yet again it comes back to diet....