Hyp3-D-Tic7-Oic8-BK (compound II), and Arg(Tos)'-Hyp3-Thi5-D-Tic7-Oic8-BK (compound III), were tested against the effects of BK in 9 bioassay preparations including visceral smooth muscles, vasoconstriction, plasma protein extravasation, release of prostaglandin E2, bronchoconstriction, and stimulation of afferent C-fibre nociceptors. In some of these tests the effects of the new compounds were compared with those of the antagonist D-Arg0-Hyp2-Thi5'8-D-Phe7-BK (compound IV), described by

1 The novel bradykinin antagonist, HOE 140, completely blocked the fall in rabbit blood pressure caused, not only by i.v. bradykinin, but also by i.v. kallikrein. This shows that both the effects of exogenously administered bradykinin and those of endogenously released kinins are antagonized by HOE 140. 2 Acute pacreatitis was induced in rats by i.v. infusion of the cholecystokinin analogue, caerulein. This treatment resulted in massive oedema of the pancreas, increased activities of amylase and lipase in serum and a characteristic, biphasic fall in blood pressure. 3 HOE 140 prevented the caerulein-induced pancreatic oedema and the second phase of hypotension whereas NPC 349, a widely used, but short-acting, bradykinin antagonist did not show a significant inhibition. HOE 140, in contrast to its inhibitory effects on caerulein-induced pancreatic oedema and hypotension, significantly augmented the increases in amylase and lipase activities in serum. 4 It is concluded that in this model of acute pancreatitis, the release of kinins induces pancreatic oedema and hypotension. Prevention by HOE 140 of the kinin-induced oedema allows the pancreatic enzymes to leave the tissue without hindrance and thus will diminish subsequent pathological events. It is suggested that the results obtained with the highly potent and long-acting bradykinin antagonist, HOE 140, provide a pharmacological basis for a clinical trial in acute pancreatitis.

1 In a previous investigation, Hoe 140, a specific and potent bradykinin B2 receptor antagonist, prevented the pancreatic oedema and the hypotension observed during acute experimental pancreatitis; however, it augmented the associated rises in the serum activities of pancreatic enzymes. Therefore, we have now investigated the consequences of the pancreatic oedema for the fate of activated enzymes released into the tissue during the course of acute pancreatitis.2 Acute oedematous pancreatitis was induced in rats, pretreated with captopril (50 pmol kg-', i.p.), by hyperstimulation of the exocrine function of the pancreas with the cholecystokinin analogue, caerulein (4 nmol kg-' h-', i.v.), for up to 120 min. 3 Pancreatic oedema began to develop 10 min after the start of the caerulein infusion, reached a maximum within about 45 min, and then declined slightly. The development of the oedema parallelled the second phase of the caerulein-induced fall in blood pressure found in earlier experiments. No further extravasation of plasma proteins occurred during the 2nd hour of the caerulein infusion. The oedema formation was completely blocked in animals pretreated with the bradykinin receptor antagonist, Hoe 140 (100 nmol kg-', s.c.). Pretreatment with aprotinin or soy bean trypsin inhibitor did not result in a significant inhibition of the oedema. 4 The haematocrit of animals with experimental pancreatitis showed a pronounced increase which started 10 min after the start of the caerulein infusion and reached maximal values at 60 min. The changes in haematocrit showed a reduction in total blood volume of 28% due to a 48% loss of plasma. This effect was completely blocked by Hoe 140. 5 In rats with caerulein-induced pancreatitis, there was a time-dependent increase in the activities of amylase and lipase in blood serum as well as in the pancreas. Pretreatment with Hoe 140 greatly augmented the caerulein-induced rise in enzyme activities in blood serum but potently attenuated it in the pancreas. The activities of trypsin in both the blood serum and the pancreas were below or near the limit of detection in all experimental groups. 6 It is concluded that the second phase of hypotension in this model of acute pancreatitis is due to the liberation of kinins which cause a massive loss of blood plasma into the pancreas and into the retroperitoneal space. Activated enzymes are trapped in the pancreas, at least in part, by the oedema of the gland. Treatment with Hoe 140 prevents the oedema formation and greatly facilitates the egress of activated enzymes from the pancreas.

Austria1 The inhibition of the bradykinin-induced plasma extravasation by six bradykinin (Bk) antagonists was tested on rabbit skin. All of them showed inhibitory effects without an agonistic action in the doses used. B4310 (Lys-Lys-3-Hyp-5,8-Thi-7-DPhe-Bk) was the most active antagonist and was therefore used in the subsequent experiments. 2 B43 10 (5-500 nM) antagonized the bradykinin-induced reduction of the venous outflow from the rabbit isolated ear in a dose-dependent manner without affecting the arterial vasoconstriction induced by angiotensin II. 3 The bradykinin-induced release of prostaglandin E2 (PGE2) from the perfused rabbit ear was reduced by 63% when B4310 (800 nM) was infused before, during and after the bradykinin injection. 4 Bradykinin was injected into the ear artery of anaesthetized rabbits and the reflex hypotensive response was used as indicator of the nociception. The response was antagonized by a local infusion of B4310 (50 and 500 nM). The antagonism was dose-dependent and reversible. The parallel shift of the dose-response curve to bradykinin suggests a competitive inhibition. However, B4310 did not antagonize acetylcholine-induced nociceptor stimulation. 5 B4310 inhibited bradykinin-induced stimulation of the trigeminal nerve which results in a substance P-mediated contraction of the iris sphincter muscle. A pA2 of 7.59 was calculated. B4310 did not inhibit capsaicin-induced contractions. 6 It is concluded that B4310 inhibits specifically five different actions of bradykinin which are related to its possible pathophysiological role.

The development of selective antagonists for bradykinin B₂ receptors has greatly advanced research on the role of the kallikrein-kinin system in acute pancreatitis. Kinins released during the course of the inflammatory injury are the major cause of the vascular symptoms, i.e. pancreatic oedema formation and its consequences, such as haemoconcentration, hypovolaemia and hypotension. Kinins are also involved in the accumulation of potentially cytotoxic factors in the pancreatic tissue. However, treatment with B₂ antagonists must begin prior to the formation of pancreatic oedema in order to inhibit or attenuate the vascular effects. Visceral pain as a possible target symptom for treatment with B₂ antagonists at later time points is suggested by the B₂ receptor-mediated activation of nociceptive afferents.