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BAT WING VENULES PUMP BLOOD
Author(s) -
Dongaonkar Ranjeet,
Meisner Joshua,
Quick Christopher,
Stewart Randolph
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a483-d
Subject(s) - venule , blood flow , blood vessel , contraction (grammar) , sodium nitroprusside , anatomy , hemodynamics , peristaltic pump , microcirculation , venous blood , arterial blood , blood pressure , chemistry , anesthesia , medicine , nitric oxide , physics , meteorology
Venomotion, spontaneous cyclic contractions of venules, was first observed in the bat wing in 1852. The question of whether venomotion propels blood remains controversial. Despite failure of common animal models which require anesthesia and surgery to provide evidence for pumping, we hypothesized that venomotion actively pumps blood in unanesthetized subjects. The wings of unanesthetized Pallid bat were examined non‐invasively using intravital microscopy. Video caliper and optical doppler velocimeter were used to measure changes in vessel diameter and blood flow in response to inhibition of venomotion by topical sodium nitroprusside (SNP). The vessel diameter‐blood velocity relationship created by active venous contractions matched the characteristics of peristaltic pumps. Venular valves working in synchrony with these contraction waves, facilitate unidirectional blood flow similar to positive displacement pumps. SNP increased venular diameter and abolished venomotion. SNP also decreased blood flow through these venules. If the venule was behaving as a passive conduit, vessel relaxation should have decreased passive resistance and increased blood flow. We conclude that venules in this animal model actively pump blood. The conventional belief that capillary pressure is proportional to the ratio of arteriolar and venular resistances assumes passive venular flow and, thus, must be re‐evaluated.