Possible embryogenetical differences of the dog venous system in sensitivity to vasoactive substances.

Abstract

Abstract-Using isolated dog veins, we examined whether correlations exist between the regional differences in sensitivity to drugs and their embryogenesis.Twelve different veins were dissected. In the analysis, the data obtained previously for the inferior vena cava were also included. Spiral strips were prepared and the contractile responses to cumulative application of norepinephrine (NE), 5-hydroxytryptamine (5-HT), histamine (Hist) and acetylcholine (ACh) were recorded isometrically.For each drug, a histogram was drawn by stacking the overlapping ranges (mean-:_S.E.) of the pD2 value for each vein. The histogram indicated the number of veins which could share the same pD2 value. We obtained the following results: (I) Veins of the body wall had high sensitivity to NE (pD2 >6.40) and 5-FIT (pD2 --6.60) and veins of the intestinal system, except for the splenic vein, were not so sensitive to NE and 5-HT, but exhibited high sensitivity to Hist (pD2 :,>4.60), (2) the middle segment of inferior vena cava responded similarly to portal and mesenteric veins; (3) the responses of splenic vein to the agents used were quite different from those of portal and mesenteric veins. These results suggest possible correlations between the responsiveness of venous smooth muscles and embryogenesis of the venous system. Previously we reported on the regional differences of canine veins in responsiveness to bradykinin, and classified the veins into high and low sensitive groups (1). Specifically, the inferior vena cava was found to be a mosaic vessel which exhibited marked segmental differences in the response to several vasoactive substances as well as differences in the histological features (2). It was further revealed that the innervation was also entirely different among the segments of the vessel (3). In the course of these investigations, re markable correlations were noted between the regional differences and the embryogenesis of the venous system. A question arises as to whether these findings can be regarded as examples having more general implications.The present study was undertaken to obtain a wider view of the problem. Comparison based on a common, simple criterion was made among various sites of dog veins regarding their sensitivity to four vasoactive agents. The veins of the intestinal system were clearly different from those of the body wall. Some notable correlations with embryogenesis, and Present address:

A Regional Difference in Endothelium-Dependent Relaxation Responses to Acetylcholine in the Canine Venous System

“…The preconstrictions evoked by me thoxamine slighly varied among the veins, but the regional difference in endothelium-depen dent relaxations were not related to the varia tion of the preconstriction levels (see, for in stance, the results of jugular vein and azygos veins in Table 1). Acetylcholine is known to cause the contractile responses in the veins showing the endothelium-dependent relaxa tions in the present study (6,9). However, the influence of such contractions on the observed relaxation responses seemed unlikely, because ACh-induced contractile responses of these veins occurred at higher concentration than 10-6 M (6, 9), whereas the endothelium dependent relaxations evoked by ACh were seen at lower concentrations than this, and maximum responses were obtained around 3x10-7 M. Thus, the present study indicated that the endothelium-dependent relaxation responses to ACh are regionally different in the canine venous system.…”

“…However, there are only a few reports de scribing the endothelium-dependent re sponses of veins (3,4). In previous papers, we repeatedly indicated that the canine venous system consists of veins characteristically different in pharmacological responses (5)(6)(7)(8)(9). Therefore, in the present study, distribution of endothelium-dependent relaxation re sponses in the venous system was inves tigated by using 15 canine veins selected systematically (5,6).…”

“…In previous papers, we repeatedly indicated that the canine venous system consists of veins characteristically different in pharmacological responses (5)(6)(7)(8)(9). Therefore, in the present study, distribution of endothelium-dependent relaxation re sponses in the venous system was inves tigated by using 15 canine veins selected systematically (5,6). Adult mongrel dogs of either sex (body weight, 7-15 kg) were anesthetized with sodium pentobarbital (35 mg/kg).…”

“…Adult mongrel dogs of either sex (body weight, 7-15 kg) were anesthetized with sodium pentobarbital (35 mg/kg). After heparin was administered to prevent the blood clotting over the inner surface of vessels, segments of veins were carefully removed from 15 different sites (5,6). The veins examined were the external jugular, cephalic, brachiocephalic, azygos, pulmonary, portal, mesenteric, splenic, renal, femoral and lateral saphenous veins, the superior vena cava.…”

Regional differences of reactivity to stimulants in the dog portal tree

“…In the dog, the splenic vein has a high sensitivity to noradrenaline and 5-hydroxytryptamine, like the veins of the body wall or extremities, and is not so sensitive to histamine unlike the main portal or mesenteric veins (Ishikawa et al, 1980). The gastric vein is said to be derived embryologically from the foregut plexus, while another portal segment derived from the vitelloumbilical veins (Butler, 1952) and the splenic vein is a shunt vein between the spleen and the portal system (Miki, 1983).…”