Measurement of muscle microvascular oxygen pressures: compartmentalization of phosphorescent probe.
OBJECTIVE
To determine whether the phosphorescent probe Oxyphor R2 (a palladium porphyrin dendrimer) becomes extravasated within normotensive skeletal muscle, R2 perfusion and washout studies were performed using a perfused rat hindlimb preparation.


METHODS
Phosphorescence signals were monitored in tibialis anterior muscles after 35 min of R2 blood perfusion and across a subsequent washout period that included vasodilation (sodium nitroprusside, SNP, approximately 3 x 10(-2) M).


RESULTS
Two responses were evident: Group 1 (n = 4)--Inflowing blood pressure and vascular conductance remained stable close to initial values and subsequently a marked vasodilation was evident with SNP (vascular conductance; R2 blood perfusion, 0.096 +/- 0.005; washout, pre-SNP, 0.085 +/- 0.005, post-SNP, 0.110 +/- 0.005 mL/min/mmHg, p <.05, for pre- vs. post-SNP). Baseline phosphorescence signals could be monitored up to 99 +/- 36 s post-SNP when the phosphorescence signal disappeared. For these muscles, palladium content was undetectable. Group 2 (n = 3)--Inflowing blood pressure increased 112% and vascular conductance fell approximately 50%. These hindlimbs were unresponsive to SNP, phosphorescence signal was undiminished by washout and SNP, and muscles became edematous.


CONCLUSIONS
These results suggest that in normotensive muscle (i.e., Group 1 above), extravasation of phosphorescent probe R2 over 35 min of perfusion is insufficient to yield a detectable phosphorescence signal in skeletal muscle.
Department of Kinesiology, Kansas State University, Manhattan, Kansas 66506-5802, USA. poole@vet.ksu.edu
David C
DC
Poole
Brad J
BJ
Behnke
Paul
P
McDonough
Richard M
RM
McAllister
David F
DF
Wilson
D000818:Animals; D001784:Blood Gas Analysis / Q000379:methods* / Q000592:standards; D005119:Extravasation of Diagnostic and Therapeutic Materials; D008163:Luminescent Measurements; D008297:Male; D008665:Metalloporphyrins; D008833:Microcirculation; D015335:Molecular Probes; D018482:Muscle, Skeletal / Q000098:blood supply*; D009599:Nitroprusside / Q000494:pharmacology; D010100:Oxygen / Q000097:blood*; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation
D008665:Metalloporphyrins; D015335:Molecular Probes; C474537:oxyphor R2; D009599:Nitroprusside; D010100:Oxygen