ABSTRACTS

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MECHANICAL FORCE APPLIED TO RAT PULMONARY ARTERIES INDUCES COGNECTIVE TISSUE BIOSYNTHESIS AND GENE EXPRESSION

Carol A. Tozzi, Ph.D., George J. Poiani, M.D., Charles D. Boyd, Ph.D., David J. Riley, M.P.

Departments of Medicine and Surgery, University of ~edicine and Dentistry of New Jersey- Rutgers Medical School, New Brunswick, New Jersey DBgo3

B7

Structural remodeling in chronic hypoxic

pulmonary hypertension involves accumula-

ti~n of connective tissue in the proximal

pulmonary artery. Increased intraluminal

pressure transmitted from upstream resis-

tance vessels may play a role in connec-

tive tissue accumulation in the proximal

pulmonary artery. TO investigate this

possibi l i ty, we measured collagen biosyn-

thesis and levels of mRNAs for matrix

proteins in isolated segments of pulmonary

arteries from 270 gm Sprague-Dawley rats

were isolated, divided into 2 segments

3mm in %ength, and each pair was placed in

a tissue bath containing Krebs Ringer

bicarbonate, I0 mEq/ml ascorbic acid, 116

mEq/ml proline, maintained at 37~C and

aerated with g5% 02-5~ CO 2. One segment

was stretched (S) using fine steel hooks

to a tension equivalent to 100 mmHg pres~

sure for 4 hr; the control segment (C) was

unstretched. Collagen biosynthesis was

estimated in 6 paired tissues by incubat- ing with I uCi/ml [14C]proline and deter-

mining tissue 14C-labelled hydroxyproline.

In 20 other paired tissues, S and C

tissues were pooled, total RNA was ex~

tracted, and levels of specific mRNA determined using 32p-labelled human cDNA

probes for pro ~I( I ) collagen (Hf 677),

elastin (pcHEL-I), and y-actin (pHFyA-I).

Actin was used as an internal standard for cellular proteins. The [14C]hydroxy-

proline was 433 ~ 127 cpm/mg protein/hr in

the S group compared to 198 ± 48 cpm/mg

protein/hr in the C group (p<O.05). The

levels of mRNA for Type I collagen,

elastin, and actin were increased in the

stretched vessels compared to control, and

there appeared to be a greater increase in

elastin than collagen mR~A levels (table).

These results indicate that short-tern

mechanical tension induces collagen bio-

synthesis and increased mRNA levels for

collagen, elastin, and actin. ~e conclude

that mechanical tension applied to pulmo-

nary vascular tissue induces va'scular

collagen biosynthesis and the increased

synthesis is regulated by gene transcrip-

tion.

Probe Control Stretched %~

Collagen 8.5 • 13.1 +54

Elastin 105 293 +179

Actin 1.0 2.4 +140

• dpm probe hybridized/ng total RNA