Table 1.

Validation of method for recovering nitrite from frozen heart tissue samples

	Extract 1 (24 h)	Extract 1 (48 h)	Extract 2 (24 h)
Nitrite concentration, nmol/l	121±25	114±29	11±6*

Values are means ± SE. Samples (∼100 mg each, n = 6) of one rat heart frozen at −80°C were powdered in the cold and extracted for 24 h into 0.5 ml nitrite-free water at 4°C. Supernatents were separated from tissue pellets and their nitrite concentrations measured immediately (extract 1, 24 h) and again after storage at 4°C for an additional 24 h (extract 1, 48 h). Tissue pellets recovered at 24 h were reextracted into fresh nitrite-free water for another 24 h (extract 2, 24 h) and measurements repeated. Extraction into water for 24 h quantitatively recovers nitrite from frozen heart tissue.

^*P < 0.01 vs. extract 1 at 24 h.