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The effect of quinidine and quinine on a potassium current (IKr)
Does IV Metolazone of IV Furosemide
Potentiate
the Diuretic
Action
The Effect of Quinidine Current (IK,)
John C. Somberg: I. Cvetanovic, W. Cao and V. Ranad Rush University and Academic Pharmaceuticals, Chicago, IL Background: Metolazone (M), an antiarrhythmic acid derivative, has diuretic action as a potent naturetic agent with minimal kaluretic activity with a dual action on the proximal tubule, as well as the cortical diluting segment. In combination with furosemide is often employed clinically when furosemide (F) alone no longer causes a brisk diuresis. Methods: To determine if M and F have a synergistic diuretic action, Sprague Dawley rats weighing between 450 - 550 grams, received an IV preparation of M or F injected IP with 24 hour urine collected. Results: Vehicle control IV caused a 9 f 1 ml/24 hrs. output l
of urine with a sodium concentration [Na]u of 194 2 41 p g/L. (n=6 per group) M 2 mg/kg resulted in 16 2 3 ml/24 hrs. and [Na]u of 278 k 76 I.@. F 2,4 or 6 mg/kg resulted
in a urine volume of 9 2 1, 14 + 2 and 17 + 2 mL/24 hrs. and wa]u of 194 + 41, 206 + 108 and 229 5 911.&L, respectively.
M
IP 4 mgikg
combined
with
F 4m&g
resulted in a urine value of 21 + 1 ml/24 hrs. and a [Na]u of 326 + 108 pg/L. Combining M + F resulted in a 50%
and Quinine
on a Potassium
John C.. Somberg’Carlos Oberti’, Bibiana Pinna*,Vasant Ranade’, ‘Rush Presbyterian-St. Luke’s Medical Center, Chicago, IL, USA ‘Facultad de Medicina,Montevideo, Uruguay Background: Quinidine (Q) is known to be a sodium channel blocker, as well as prolonging the QT interval through blocking potassium current. Studies were performed with Q and the l-isomer quinine (QN) to evaluate the relative activities of these two compounds on potassium current. Methods: HERG currents were obtained by injection of cRNA into Xenopus oocytes. Recordings were made with an external [Kf] of 5 mM, -80 mV of holding potential and test potentials of 1200 ms in steps of 10 mV from -50 to +40 mV. The peak current was measured at 30 mV. The effects of Q and QN were studied at 10m6,1Om5and 1Oa M. Results: The I CsOfor HERG block was 6.4 + 1.9 pmol/L 80.2 + 2.1 pmol/L for QN. At 0.33 Hz for Q and stimulation frequency, the percent block for Q was 33 + 6 ( 10e6M) , 42 k 2 ( 10e5M) and 83 5 2 (“‘M). The percent block for QN was 10 t 3 (lO”M), 21 k 6 (10.‘M) and 52 + IO (lOAM). Conclusion: Quinidine, the d-isomer, blocks HERG current
increase in urine volume and a 58% increase in urine sodium content, P
and does it considerably more (12.5 times) than the l-isomer quinine. The current block is dose dependent for both Q and QN. The difference in current block may explain the higher
DISTRIBUTION AND TEMPORAL EXPRESSION OF FIBROBLAST GROWTH FACTOR-16 IN THE HEART David P. Sontag and Peter A. Cattini. Department of Physiology, University of Manitoba, Winnipeg, Canada.
PADRENERGIC STIMULATION SYNCHRONIZES INTRACELLULAR CA’+ RELEASE DURING E-C COUPLING IN HEART CELLS
was then used to identify a peptide that was used to generate antibodies against FGF-16. As part of the antibody characterization, recombinant mouse FGF-16 protein (polyhistidine-tagged) was generated using a bacterial expression
system. The anti-sera compared
from two rabbits
to be specific
to closely
(#61660
for both mouse
related FGF-9
(78%)
and #61661)
and human
and prototypic
were
FGF-16,
FGF-2
(40.2% identity) when tested by protein (western) immunoblot analysis. Antibodies were then utilized to probe western blots containing protein samples from various adult mouse tissues including heart,
lung,
liver,
protein. 40 kD), purified day 17
brain
and kidney
and were
assessed
for
seen
LongSheng Song, Shi-Qlang Wang, Edward G lakatta, Heplng Cheng. Lab. of Cardiovasc. Sci., GRC, NIA, NIH, Baltimore, USA
The heparin-binding tibroblast growth factor (FGF) family is extensive, consisting of at least 23 members, some of which have been demonstrated to he important in cardiac development and remodeling. Information based on the detection of transcripts for the 16’” member of this family (FGF-16) suggests that its distribution is unique to the heart in the postnatal rat. We sought to extend the characterization of FGF-16 in the postnatal heart by examining the distribution and developmental expression of FGF-16 protein in the mouse. We have cloned the mouse cDNA coding for FGF-16 and determined its putative protein sequence (GenBank Accession #AF292104). The sequence
determined
incidence of proarrhythmia with Torsade de pointes with quinidine therapy as contrasted to quinine.
FGF-16
Two bands were observed in the heart samples (-32 and the smaller band being more intense and consistent with FGF-16 (28 kD). Mouse heart samples from embryonic
To elucidate microscopic mechanisms underlying modulation of cardiac excitation-contraction (EC) coupling by @ adrenergic receptor (AR) stimulation, we examined local Ca” release function, i.e., “Ca” spikes” at individual T tubule-SR (T-SR) junctions, using confocal microscopy and our recently developed technique for release flux measurement (J. Phvsiol. Sona L. et al, 1998). We found that B-AR stimulation by -norepineihrine plus an.al-adrenergic blocker, prazosin, increased the amplitude of SR Ca”. release flux (JAR), its running integral (JJsR), and L-type Ca” channel current (1~~). and shifted their bell-shaped voltage-dependence leftward by -10 mV, with the relative effects ranking Ic.>JsR>JJsR. Confocal imaging revealed that the bell-shaped voltagedependence of SR Ca” release is attributable to a graded recruitment of T-SR junctions as well as to changes in Ca” spike amplitudes. P-AR stimulation increased the fractional T-SR junctions that fired Ca2+ spikes and augmented Ca” spike amplitudes, without altering the SR Ca” load, suggesting that more release units were activated synchronously among and within T-SR junctions. Moreover, P-AR stimulation decreased the latency and temporal dispersion of Ca2’ spike occurrence at a given voltage, delivering most of the Ca” at the onset of depolariiation rather than spreading it out throughout depolarization. Our data suggests that synchronization of SR Ca*’ release represent a heretofore unappreciated mechanism of P-AR modulation of cardiac inotropy.
and 10 week adult were also analyzed for FGF-16 expression. Analysis of westerns by densitometry revealed that the more prominent 32 kD band was at least 10 fold higher in the adult when compared with that of the embryonic heart. All3
Potentiate
the Diuretic
Action
The Effect of Quinidine Current (IK,)
John C. Somberg: I. Cvetanovic, W. Cao and V. Ranad Rush University and Academic Pharmaceuticals, Chicago, IL Background: Metolazone (M), an antiarrhythmic acid derivative, has diuretic action as a potent naturetic agent with minimal kaluretic activity with a dual action on the proximal tubule, as well as the cortical diluting segment. In combination with furosemide is often employed clinically when furosemide (F) alone no longer causes a brisk diuresis. Methods: To determine if M and F have a synergistic diuretic action, Sprague Dawley rats weighing between 450 - 550 grams, received an IV preparation of M or F injected IP with 24 hour urine collected. Results: Vehicle control IV caused a 9 f 1 ml/24 hrs. output l
of urine with a sodium concentration [Na]u of 194 2 41 p g/L. (n=6 per group) M 2 mg/kg resulted in 16 2 3 ml/24 hrs. and [Na]u of 278 k 76 I.@. F 2,4 or 6 mg/kg resulted
in a urine volume of 9 2 1, 14 + 2 and 17 + 2 mL/24 hrs. and wa]u of 194 + 41, 206 + 108 and 229 5 911.&L, respectively.
M
IP 4 mgikg
combined
with
F 4m&g
resulted in a urine value of 21 + 1 ml/24 hrs. and a [Na]u of 326 + 108 pg/L. Combining M + F resulted in a 50%
and Quinine
on a Potassium
John C.. Somberg’Carlos Oberti’, Bibiana Pinna*,Vasant Ranade’, ‘Rush Presbyterian-St. Luke’s Medical Center, Chicago, IL, USA ‘Facultad de Medicina,Montevideo, Uruguay Background: Quinidine (Q) is known to be a sodium channel blocker, as well as prolonging the QT interval through blocking potassium current. Studies were performed with Q and the l-isomer quinine (QN) to evaluate the relative activities of these two compounds on potassium current. Methods: HERG currents were obtained by injection of cRNA into Xenopus oocytes. Recordings were made with an external [Kf] of 5 mM, -80 mV of holding potential and test potentials of 1200 ms in steps of 10 mV from -50 to +40 mV. The peak current was measured at 30 mV. The effects of Q and QN were studied at 10m6,1Om5and 1Oa M. Results: The I CsOfor HERG block was 6.4 + 1.9 pmol/L 80.2 + 2.1 pmol/L for QN. At 0.33 Hz for Q and stimulation frequency, the percent block for Q was 33 + 6 ( 10e6M) , 42 k 2 ( 10e5M) and 83 5 2 (“‘M). The percent block for QN was 10 t 3 (lO”M), 21 k 6 (10.‘M) and 52 + IO (lOAM). Conclusion: Quinidine, the d-isomer, blocks HERG current
increase in urine volume and a 58% increase in urine sodium content, P
and does it considerably more (12.5 times) than the l-isomer quinine. The current block is dose dependent for both Q and QN. The difference in current block may explain the higher
DISTRIBUTION AND TEMPORAL EXPRESSION OF FIBROBLAST GROWTH FACTOR-16 IN THE HEART David P. Sontag and Peter A. Cattini. Department of Physiology, University of Manitoba, Winnipeg, Canada.
PADRENERGIC STIMULATION SYNCHRONIZES INTRACELLULAR CA’+ RELEASE DURING E-C COUPLING IN HEART CELLS
was then used to identify a peptide that was used to generate antibodies against FGF-16. As part of the antibody characterization, recombinant mouse FGF-16 protein (polyhistidine-tagged) was generated using a bacterial expression
system. The anti-sera compared
from two rabbits
to be specific
to closely
(#61660
for both mouse
related FGF-9
(78%)
and #61661)
and human
and prototypic
were
FGF-16,
FGF-2
(40.2% identity) when tested by protein (western) immunoblot analysis. Antibodies were then utilized to probe western blots containing protein samples from various adult mouse tissues including heart,
lung,
liver,
protein. 40 kD), purified day 17
brain
and kidney
and were
assessed
for
seen
LongSheng Song, Shi-Qlang Wang, Edward G lakatta, Heplng Cheng. Lab. of Cardiovasc. Sci., GRC, NIA, NIH, Baltimore, USA
The heparin-binding tibroblast growth factor (FGF) family is extensive, consisting of at least 23 members, some of which have been demonstrated to he important in cardiac development and remodeling. Information based on the detection of transcripts for the 16’” member of this family (FGF-16) suggests that its distribution is unique to the heart in the postnatal rat. We sought to extend the characterization of FGF-16 in the postnatal heart by examining the distribution and developmental expression of FGF-16 protein in the mouse. We have cloned the mouse cDNA coding for FGF-16 and determined its putative protein sequence (GenBank Accession #AF292104). The sequence
determined
incidence of proarrhythmia with Torsade de pointes with quinidine therapy as contrasted to quinine.
FGF-16
Two bands were observed in the heart samples (-32 and the smaller band being more intense and consistent with FGF-16 (28 kD). Mouse heart samples from embryonic
To elucidate microscopic mechanisms underlying modulation of cardiac excitation-contraction (EC) coupling by @ adrenergic receptor (AR) stimulation, we examined local Ca” release function, i.e., “Ca” spikes” at individual T tubule-SR (T-SR) junctions, using confocal microscopy and our recently developed technique for release flux measurement (J. Phvsiol. Sona L. et al, 1998). We found that B-AR stimulation by -norepineihrine plus an.al-adrenergic blocker, prazosin, increased the amplitude of SR Ca”. release flux (JAR), its running integral (JJsR), and L-type Ca” channel current (1~~). and shifted their bell-shaped voltage-dependence leftward by -10 mV, with the relative effects ranking Ic.>JsR>JJsR. Confocal imaging revealed that the bell-shaped voltagedependence of SR Ca” release is attributable to a graded recruitment of T-SR junctions as well as to changes in Ca” spike amplitudes. P-AR stimulation increased the fractional T-SR junctions that fired Ca2+ spikes and augmented Ca” spike amplitudes, without altering the SR Ca” load, suggesting that more release units were activated synchronously among and within T-SR junctions. Moreover, P-AR stimulation decreased the latency and temporal dispersion of Ca2’ spike occurrence at a given voltage, delivering most of the Ca” at the onset of depolariiation rather than spreading it out throughout depolarization. Our data suggests that synchronization of SR Ca*’ release represent a heretofore unappreciated mechanism of P-AR modulation of cardiac inotropy.
and 10 week adult were also analyzed for FGF-16 expression. Analysis of westerns by densitometry revealed that the more prominent 32 kD band was at least 10 fold higher in the adult when compared with that of the embryonic heart. All3