Although angiotensin II (Ang II) has been implicated in the pathophysiology of congestive heart failure, its temporal and regional changes during the development and progression of the disease are poorly defined. Our objective was to assess circulating, renal, cardiac, and vascular Ang II in a canine model of rapid ventricular pacing-induced heart failure that evolves from early left ventricular dysfunction to overt congestive heart failure. Ang II was measured by radioimmunoassay with low cross-reactivity to other angiotensins. Control, early left ventricular dysfunction, and overt congestive heart failure dogs were studied. Early left ventricular dysfunction was characterized by impaired cardiac function, cardiac enlargement, preserved renal perfusion pressure, maintained urinary sodium excretion, and normal plasma renin activity. Overt congestive heart failure was characterized by further impaired cardiac function and cardiac enlargement, reduced renal perfusion pressure, urinary sodium retention, and increased plasma renin activity and plasma Ang II. In early left ventricular dysfunction dogs, renal cortical, renal medullary, ventricular, and aortic Ang II were unchanged, and atrial Ang II was decreased. In overt congestive heart failure dogs, Ang II was increased in the kidney and heart compared with normal dogs and in all tissues compared with early left ventricular dysfunction dogs. The greatest increase in tissue Ang II occurred in the renal medulla. We conclude that early increases in local renal, myocardial, and vascular Ang II do not occur in this model of early left ventricular dysfunction and may even be suppressed. In contrast, increased myocardial and particularly renal Ang II in association with increased circulating Ang II are hallmarks of overt experimental congestive heart failure. These studies provide new insights into the temporal and regional alterations in Ang II during the progression of experimental congestive heart failure.

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Leu-Met-NHJ, a tachykinin and putative pain transmitter found in the spinal cord, is one of an increasing number of peptides which are known to function as intracellular messengers, i.e., neurotransmitters, in the nervous system. Endogenous peptide neurotransmitters are usually quantitated by radioimmunoassay (RIA), the basis of which is a saturable, high-affinity binding of the neuropeptide to an antibody.' This immunological method affords high sensitivity (fmol range) of analysis but lacks complete specificity due to cross-reactivity of the antibody with substances other than the peptide of interest. For example, the limit of detection of substance P by RIA is generally less than 1 fmol, but the antibody used in the RIA analysis crossreacts with oxidized substance P (Arg-Pro-Lys-Pro- Moreover, assessment of possible cross-reactivity can only be made if the appropriate peptide structure is already known, and if that peptide is available for testing. We have developed a strategy for the quantitative analysis of endogenous substance P which couples immunological methods with the sensitivity and specificity of on-line microcolumn (capillary) liquid chromatography/continuous-flow fast-atom bombardment (dynamic-FAB) mass spectrometry in the selected-ion monitoring (SIM) mode. The aim was not to attempt to replace established RIA protocols, but to obtain complementary information which would confirm the identification of the immunoreactivity . This strategy is detailed below. , a flow rate of 1 mL/min, and UV detection at 220 nm. The retention time of substance P under these conditions was 33.5 min. The purified deuterated peptide was then characterized by fast-atom bombardment mass spectrometry (8 keV xenon, matrix-5 : 1, DTT + DTE). The base peak was the protonated molecule. Gln EXPERIMENTAL Extraction and immunoaffinity purification of substance P from cat spinal cordCat spinal cords were weighed and 0.1 N HCI was added to produce a final concentration of 0.05 g/mL.The mixture was boiled for 10 min, homogenized, concentrated in uacuo, then dissolved in phosphate-

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