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Children's Research Institute, Children's Hospital, and Division of Neonatology, Department of Pediatrics, Ohio State University, Columbus, Ohio 43205
Previous attempts to determine
developmental changes in the vascular myogenic response have been
confounded by the presence of competing vasoactive stimuli or the use
of isolated vessels with markedly different baseline diameters. To
circumvent these issues, small mesenteric arteries (diameter ~150
µm) from 1- and 10-day-old piglets were studied in vitro under
no-flow conditions. In situ studies demonstrated that the intravascular
pressure and diameter of these vessels were similar in both age groups,
allowing an effective comparison of the myogenic response not obscured by differences in basal diameter. The pressure-diameter relationship was age specific. Thus, although small mesenteric arteries from both
age groups demonstrated myogenic constriction in response to stepwise
increases in pressure (0 to 100 mmHg, in 20-mmHg increments), the
intensity of contraction was significantly greater in vessels from
1-day-old piglets particularly within the pressure range normally
experienced by these vessels in situ. Attenuation or activation of PKC with calphostin C or indolactam, respectively, substantially altered the pressure-diameter relationship in 1-, but not
10-day-old arteries; thus calphostin C essentially eliminated the
contractile response to pressure elevation in younger subjects, whereas
indolactam significantly increased the intensity of the myogenic
response and shifted its activation point to a lower pressure range.
Immunoblots carried out on protein recovered from these arteries
revealed the presence of
,
,
,
, and
; notably, expression of the
- and
-isoforms substantially decreased between postnatal days 1 and 10.
newborn intestine; intestinal circulation
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