In vivo effects of the controlled NO donor/scavenger ruthenium cyclam complexes on blood pressure.

Ruthenium(II/III) complexes able to bind and release NO* were tested in vivo, in conscious Wistar rats instrumented for continuous blood pressure (BP) measurement and administration of in bolus injections (5 to 100 nmol/Kg i.v.) of trans-[Ru(II)Cl(NO+)(cyclam)](PF6)2 (cyclam-NO) or sodium nitroprusside (SNP). For normotensive rats, cyclam-NO produced a sustained 10% BP reduction of basal MAP during 7 +/- 0.4 to 11 +/- 0.3 min. In acute hypertensive rats, cyclam-NO produced BP reduction 3-fold larger than in normotensive rats and similar to that of SNP (maximal effect: 41 +/- 1.3 vs. 45 +/- 2.2 mmHg, respectively). However, the duration of the effect of cyclam-NO was 13 to 21-fold longer than that of SNP. The hypotensive effect of cyclam-NO was fully blocked in presence of continuous infusion of a NO* scavenger, carboxy-PTIO (6 mmol/Kg/min), or of the inhibitor of cGMP activation, methylene blue (83 nmol/Kg/min), or of the cyclam-NO precursor, trans-[RuCl(tfins)(cyclam)](tfms) (cyclam-tfms) (500 mmol/Kg/min). The long lasting BP reduction of cyclam-NO can be interpreted in terms of a slower rate of NO* release (k-NO = 2.2 x 10(-3) S(-1) at 35 degrees C) following chemical reduction (E(0') = 0.10 V vs NHE). In summary, cyclam-NO showed an hypotensive effect around 20 times longer than SNP in either normotensive or hypertensive rats, which was completely inhibited by methylene blue or carboxy-PTIO. Continuous infusion of cyclam-tfms completely blocked the hypotensive effect of cyclam-NO by scavenging the NO* released by the reduced cyclam-NO.

Tonin expression in the rat brain and tonin-mediated central production of angiotensin II.

Tonins are serine proteinases mainly found in the rat submandibular gland, which are capable of generating the pressor octapeptide angiotensin II (Ang II) not only from the classical substrate angiotensin I but also from the synthetic tetradecapeptide (AG(1-14)) and from angiotensinogen. In this work, tonin expression levels were evaluated in astrocytes and brain areas of the rat. By two different techniques (ribonuclease protection assay and reverse transcription-polymerase chain reaction), we could verify the presence of tonin mRNA in astrocytes and in the thalamus of the rat brain. Sequencing of the amplified brain cDNA determined it to be identical to that found in the submandibular gland. Central microinjection of tonin produced a transient (10-20 min) elevation of blood pressure and heart rate and induced water and saline intake within the first 10 min after injection. Urinary volume and salt excretion increased within 7 h after tonin injection. These effects were partially blocked by previously administered losartan, indicating that tonin effectively induced a central Ang II formation. Our data suggest that tonin may be an alternative pathway to Ang II generation in the brain and could participate in the physiological effects exerted by Ang II such as water and saline intake and blood pressure elevation.