Durwood J. Smith

Reactions of the Isolated Surviving Coronary Artery to Epinephrine, Acetylcholine and Histamine

Summary 1. The method of employing angioplethysmokymography to evaluate the responses of coronary arteries to several drugs is described. 2. Epinephrine did not produce a uniform response in the coronary arteries examined. The relation of this inconsistency to the state of vasodilation of the specimen artery is discussed. 3. Acetylcholine was found to produce consistent coronary vasoconstriction in man, pig and sheep. 4. Histamine uniformly produces vasconstriction of the coronary arteries of man, pig, ox and sheep.

In Vitro Studies of the Coronary Arteries of Man and Swine as Demonstrated by a New Technic, Angioplethysmokymography

A new in vitro technic for the study of isolated surviving arteries and veins is described. Observations of the reactivity of 21 human and 68 swine coronary arteries to histamine, acetylcholine, l-epinephrine and l-norepinephrine are reported. Histamine and acetylcholine uniformly caused vasoconstriction of the coronary arteries of man and swine. Three potential mechanisms of coronary artery vasoconstriction in these species are suggested. The blocking action of antihistaminic drugs on vasoconstriction due to histamine, and of atropine on vasoconstriction due to acetylcholine is demonstrated. It is suggested that combined therapy with these drugs may be useful in treatment of diseases of the coronary arteries.

In vitro action of cortisone on vasoconstriction due to histamine.

Summary 1. Cortisone accelerates the recovery of vascular smooth muscle from vasoconstriction due to histamine. 2. This probably represents an action of cortisone on the histamine inactivating enzyme systems.

Comparative reactivity of isolated surviving coronary arteries to l-epinephrine and l-norepinephrine.

Summary 1. l-norepinephrine and l-epinephrine produce vasodilation of the isolated surviving coronary arteries of swine. 2. 1-norepinephrine produces about 2^4 times the degree of vasodilation produced by l-epinephrine in the same artery in the same dose. This difference exceeds the anticipated difference attributable to differing molecular weights.

Pressure measurements in perfused segments of small blood vessels.

Summary A method is described for recording in vitro pressure responses from perfused segments of small blood vessels. The method permits accurate evaluation of the relationships between dose and response. For arterial biopsy specimens from the dogs mesentery, maximal pressure responses of 200 to 300 mm Hg are obtained with test doses of epinephrine at an intravascular concentration of about 1.0 γ/ml. The threshold for response is about 0.04 γ/ml. The latent period for chemical stimulation of these specimens is approximately 3 to 4 seconds.

SUBACUTE AND LATE CARDIOVASCULAR SEQUELAE TO LOW DOSES OF GAMMA RADIATION

A battery of in vivo and in vitro tests of cardiovascular performance were used to assess the effects of wholebody gamma radiation (cobalt-60) upon the cardiovascular system of dogs. A new method for study of the pressurevolume relations of isolated surviving arteries is described. Groups of six beagles were exposed to 30 r and 100 r 22 months before death and compared with littermate controls. No differences between irradiated and control dogs could be demonstrated. Eight mongrel dogs received 300 r 30 days before death and were compared with five mongrel controls. The only significant difference observed was in the pressure-volume curves of arteries from irradiated dogs, these vessels having a greater initial tone than control arteries. It is concluded that 30 r and 100 r of wholebody gamma radiation have no demonstrable effect upon the cardiovascular system of dogs irradiated 22 months before study, but that 300 r of gamma radiation does produce a significant abnormallty of blood vessels. (auth)