Effect of verapamil on pulmonary and eicosanoid responses to endotoxin in awake sheep

Plasma concentrations of type II phospholipase A2, cytokines and eicosanoids in patients with burns

The plasma concentrations of type II phospholipase A2 (type II PLA2) and eicosanoids, such as leukotriene B4 (LTB4), 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), and thromboxane B2 (TXB2), were determined by radioimmunoassay in 23 patients with burns covering at least 20 per cent of their body surface. Cytokines such as tumour necrosis factor-alpha (TNF-alpha), interleukin 6 (IL-6) and interleukin 8 (IL-8) were determined by enzyme-immunosorbent assay. There was no increase in type II PLA2 concentration in the early stage of burns, but an increase in type II PLA2 concentration was triggered by infection (P < 0.0001). The level of type II PLA2 was significantly higher in the non-surviving group than in the surviving group (P = 0.0006), suggesting that it reflects the severity of the disease. There was a significant correlation between the maximum level of type II PLA2 and TNF-alpha (r = 0.6346, P = 0.0011). There was a significant correlation between the maximum level of type II PLA2 and the accompanying plasma concentrations of LTB4, 6-keto-PGF1 alpha, and TXB2 throughout the observation period (r = 0.4814, P = 0.0200; r = 0.5943, P = 0.0028; r = 0.4368, P = 0.0372 respectively). Plasma levels of LTB4, and TXB2 were significantly higher in the burn patients who died than in those who survived (P = 0.0493; P = 0.0493 respectively).

Cecal ligation and puncture is associated with pulmonary injury in the rat: role of cyclooxygenase pathway products

The present studies evaluated the role cyclooxygenase products play in bacterial sepsis induced pulmonary injury in the rat. Lung injury was assessed by determining the pulmonary capillary filtration coefficient (Kf) and the lung lavage protein concentration four and 18 hours after cecal ligation and puncture. Four hours after cecal ligation, the Kf was unchanged from control, however, by 18 hours, the Kf was increased 171% (p < .05). Similarly, lung lavage protein levels were unchanged four hours after cecal ligation but were significantly (p < .05) elevated at 18 hours. On the other hand, pulmonary lavage immunoreactive thromboxane B2 (iTXB2) levels were increased both four and 18 hours after the initiation of sepsis. In order to determine if cyclooxygenase products played a role in the sepsis associated lung injury, ibuprofen was administered prior to cecal ligation. Ibuprofen pretreatment prevented the sepsis associated increase in both Kf and lung lavage protein concentration. These studies suggest that bacterial sepsis in the rat is associated with pulmonary injury and that early administration of ibuprofen ameliorates this damage.

Effect of verapamil on monocrotaline-induced pulmonary artery hypertension and endothelial cell dysfunction in rats

Verapamil, a calcium channel blocker has been used with partial success in cases of primary pulmonary hypertension, as well as to reduce hypoxia-induced pulmonary hypertension (PH) in rats. However, its effect on monocrotaline (MCT)-induced PH in rats is not known. We studied the effect of verapamil on MCT-induced PH. Three weeks after a single injection of MCT, significant PH was noted in the MCT-injected rats compared with control (44.35 +/- 3.5 vs. 22 +/- 2.5 mmHg). MCT-injected rats on daily verapamil showed significant reduction in PH (31.5 +/- 3.4 mmHg). The main pulmonary artery of MCT-injected rats revealed subendothelial thickening, thinning and fragmentation of elastic laminae, smooth muscle cell hypertrophy and necrosis or loss of smooth muscle cells, and increased amounts of collagen in media and adventitia. In contrast, the main pulmonary artery of MCT + VP-treated rats showed less intimal thickening, some smooth muscle cell hypertrophy, but little necrosis or loss of cells in addition to disappearance of outer elastic laminae. Smaller pulmonary arteries (less than 150 microns in diameter) in MCT + VP-treated rats showed less medial thickening than MCT groups. However, diminished lung angiotensin-converting enzyme activity suggestive of endothelial cell dysfunction was noted in both MCT and MCT + VP-treated rats. This study indicates that verapamil attenuates MCT-induced PH, but has no effect on pulmonary endothelial cell dysfunction.

Verapamil and indomethacin attenuate endotoxin-induced anorexia

To characterize the mechanism of the anorexia during infection, we investigated the effect of E. coli lipopolysaccharide (LPS) on feeding in rats under various conditions: LPS (125, 100, 75, and 50 micrograms/kg body weight = b. wt.) injected intraperitoneally (IP) reduced food intake by decreasing meal frequency without affecting meal size. The Ca++-channel blocker verapamil (5 mg/kg b. wt., IP) or the antipyretic and antiphlogistic drug indomethacin (2.5 mg/kg b. wt., IP), but not combined alpha- and beta-adrenergic receptor blockade by IP phentolamine plus propranolol (500 micrograms/kg b. wt., each) attenuated the anorectic effect of LPS (125 or 100 micrograms/kg b. wt.). The results suggest that a phospholipase A2-sensitive mechanism contributes to the anorexia during injection.

An investigation into the effects of bacterial lipopolysaccharide on human platelets

The addition of lipopolysaccharide (LPS) from Gram-negative bacteria to whole blood induced a consistent enhancement of platelet impedance aggregation (WB-PIA) and an increase in median platelet volume (MPV). In contrast, the addition of LPS to platelet rich plasma (PRP) resulted in inconsistent changes in turbidometric platelet aggregation (TPA) and no significant change in MPV. The LPS-induced increase of MPV in whole blood was inhibited by verapamil, a calcium channel blocker. We conclude that: (a) LPS consistently activates platelets in whole blood but not in PRP; (b) LPS-induced activation of platelets is probably mediated by products released by leucocytes and/or erythrocytes; (c) the increase in MPV induced by LPS is probably dependent upon calcium influx; and (4) an increase in MPV may be a useful and sensitive model for the study of platelet activation by LPS, in vitro and in vivo.