None of the sources say thereâs endothelial cell contraction specifically on the venous side. Other cards already handle histamine causing increased vascular permeability
I think the issue here is that the card makes it sound like histamine causes venoconstriction via smooth muscle contraction, like what youâd see with αâ stimulation from norepi or during exercise. But the actual mechanism that I think that other user is trying to emphasize is endothelial cell contraction in postcapillary venules being what allows for the fluid/protein leakage, not a change in tone.
I know other cards may already address the permeability piece, but for someone still learning, this distinction really matters â because if you take âvenous constrictionâ at face value, it suggests the wrong mechanism, and that can lead to a completely different (and incorrect) understanding of how histamine contributes to edema. Mechanistically, it wouldnât even make much sense.