Enhanced skin reactivity to platelet-derived permeability factor (PDPF) and exogenous histamine in an acute phase rabbit model.

Rabbits made acute phase by sub-cutaneous trauma with 2% croton oil (in mineral oil) were tested by intradermal (ID) injection with platelet-granule extracts containing platelet-derived permeability factor (PDPF). Compared with controls, skin reactivity to PDPF was enhanced in acute phase animals 3-7 days post-trauma, a period of acute inflammation as reflected by the occurrence in the circulation of C-reactive protein; maximal skin responses were observed 3-4 days post-trauma. Individual skin sites reached maximum intensity 15 min-1 hour post-ID injection of PDPF and were sensitive to chlorpheniramine maleate, suggesting a major role for histamine. Intradermal injection of histamine revealed that acute phase animals yielded an initially more intense skin reaction, and were markedly less capable of recovering from the effects of histamine. These data suggest that in the acute phase, there exists a heightened and prolonged sensitivity to the action of histamine which can be exploited by pro-inflammatory agents such as PDPF.