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Glucagon and Aminophylline as Pulmonary Vasodilators in the Calf with Hypoxic Pulmonary Hypertension
same satellite cell. It is suggested that the clusters of granule-containing cells in the lungs of cats call release the amine content of the vesicles. It is possible that this released ..i mine moderates transmission through the peribronchial ganglia ncar the site of release or at some distance from that site. It is also possible that the amine affects the activity of chemoreceptor nerve fibers of other sensory receptors that are supplied with blood from the bronchial circulation. These granule-containing cells may playa role in mediating or modulating the response to hypoxia in the cat,
Glucogon
3mg
160
.=E
.:a
140 120 100 110 100
90
Glucagon and Aminophylline as Pulmonary Vasodilators in the Calf with Hypoxic Pulmonary Hypertension *
..
80
:r
'10
E E
60 SO
40 30
Cerakl E. Bisuard, D.V.M., and James A. lVill, D.V.M.
T
he cardiovascular actions of glucagon and aminophylline han> been related to increasing intracellular levels of 3'5' cyclic adenosine monophosphate (cA~IP). The mode of activity of the ;2 agents differs: glucagon increases cA~1P bv increasing: the activitv of adenvlcyclase.' while ~inophylline and other methyl xanthines increase cAMP hy inhibiting phospbodicsterase" which is the enzyme which breaks down cA~fP to 5' A\IP. Some of the effects of increasing intracellular cA\fP are poteutiallv beneficial in certain cardiovascular diseases. These effects would include a positive inotropic and chronotropic' activity along with relaxation of contracted vascular smooth muscle.":' Wo wished to test the hypothesis that these 2 agents, glucagon and aminophylline operating by separate mechanisms to increase cA~lP, will reduce hypoxic pulmonary vasoconstriction. Calves were selected for this study because chronic airway hypoxia produces SIlS~ rained pulmonary hypertension which may lead to cor pulmonale (Brisket disease}." Furthermore. pulmonary hypertension is due to pulmonary vasoconstriction, and this is a reversible process as demonstrated by the fact that when chronic hypoxia is relieved, the vasoconstriction disappears and there is reversal of the pulmonary hypertension. Thus, cattle at high altitude provide an ideal situation for testing the action of potential pulmonary vasodilators. One additional advantage of the calf is that one may study these animals in the uvvakc, unsedated state, thus eliminating the effects of anesthesia on results ohtuined. Five calves were studied after 4 weeks of exposure at an altitude of 3,400 m (PH 510 mm Ilg). At this time, all calves had developed hypoxic pulmonary hypertension. At different times the calves were given either a single intravenous injection of aminophylline (5 mgkg) or a single intravenous injection of glucagon (3 mg). "From the L'niversitv of wtsconstn, Madison. Reprint request_\: ti« Bisgard. "eterinary Science Denartment. Unicersitn of '\·i.\'cDtlsin, Madison .53706
CHEST 71: 2, FEBRUARY. 1977 SUPPLEMENT
20
1~~~-' ; "'0
200
- -'- ...
~._._
•. _._._._.-._ ..
100
11.0 lO.O
...E
!
9.0
B.O 7.0 6.0 51015202530
40
MINUTES AnER INJECTION FIGL'RE 1. Data from bolus intravenous injection of 3 mg of glucagon. Solid circles and lines represent the data from 5 calves at 3,400 m. Vertical bars are cr; I SE~f. Open circles and dashed lines are data from 2 calves studied at sea level. C designates control prior to drug injection. HR = heart rate, P;;;, = mean aortic blood pressure, Pf:\ ::::: mean pulmonary arterial pressure, TPuR :.= total pulmonary vascular reststance. CI :;:: cardiae index.
Glucagon (Fig 1) caused a significant fall in total pulmonary vascular resistance (TPuR) brought about by both an increase in cardiac output (Cl ) and a fall in mean pulmonary arterial pressure (Pi'].) which were sustained for at least 20 minutes (control Pi'A ~ 64 rom Hg, minimum PI':, = 45 mm II~, P < O.O.?). Total peripheral resistance (TPeR) and mean aortic pressure (P,m) were also reduced while heart rate was significantly elevated by the bolus injection of glucagon. The pattern of response was similar at sea level except that TPuR and Pi':", were not altered.
19TH ASPEN LUNG CONFERENCE 263
AMINOPHYlllINI
In the sea level study no change in Pp-::'\ occurred, while there was a large decrease in the chronically hypoxic calves (control Pi':\ :::; H3 mm H~, average infusion Pi'A -- 46 mm lIg, P < 0.(1). Accordingly. TPuR was reduced by a larger magnitude in studies at 3,400 m as compared to sea level. There were no changes in arterial blood gases or acid-base balance induced by glucagon. Wtth the exception of heart rate changes in the altitude calves actions of glucagon were sustained throughout the period of infusion. In summary both glucagon and aminophylline caused reductions in TPuR. but with glucagon this was brought about by hoth an increase in CI and a fall in Pp:"\ while with aminophylline this occurred primarily by a reduction in pp\. Our data support our hypothesis that both aminophylline and glucagon are vasodilators in the presence of chronic hypoxic pulmonary vasoconstriction. The increased CI with glucagon in these calves was probably related to the knO\\11 positive' inotropic and chronotropic effects of this agent. The comparable increases in CI between spa level and high altitude indicates that chronic hypoxia does not depress the inotropic effect of glucagon. However. the reduction in maximum heart rate and failure to sustain a rapid heart rate during glucagon infusion in the chronically hypoxic calves suggests that chronotropic effects of glucagon may be par-
SmgJkg
140
.~
120
.ii 100
160 140
120 100
160
.~
S.O
140 120
A
c
,5 ~l.a~1 ,1
Jnutes
M)
100
15 1
80
after injeot'iCM"l
FI(;Ul\E2. Data from bolus intravenous injection of 5 mg kz of aminophylline. See legend, Figure 1, for definition of svmbols.
Aminophylline (Fig 2) injection caused a transient rise in heart rate and P;w while PP1 fell (control PF,\ 68 mm Hg, minimum Pj>A 51 mm Hg, P < 0.0.5). Maximal effects of pressures and heart rate occurred within the first minute of infusion of aminophylline and the reduction in pr;\ was sustained for only 10 minutes after infusion. TPuR decreased by a fall in Pp:\ with little change in CI. 1':0 changes in blood gases or acidbase balance were induced by either drug. In a second set of experiments 6 calves were studied at sea level and after 4 to 6 weeks at 3,400 m prior to and during a 3 hour infusion of glucagon at the rate of 0,10 to 0.15 mgvkgthr (Fig 3 and 4). Significant increases in heart rate occurred in both sea level and altitude studies; however, in the chronically hypoxic calves the increase in heart rate was significantly less than in sea level calves (mean maximum heart rate at sea level :::; 160 beats per minute, vs 134 beats per minute at high altitude) and was not sustained throughout infusion as it was in sea level studies. The increase in CI and decreases in P AO were comparable in sea level and high altitude studies.
=
264
=
19TH ASPEN LUNG CONFERENCE
10.0 M
0.0
C,
E
~
..0 7••
•. 0
c
LI.
0.5 HOURS of
~
INFUSiON
0.5 PI
3. Data from continuous infusion of 0.10 to 0.15 mgk~ .hr of glucagon in.6 calves at sea level. See legend. Figure 1, 'for definition of symbols, Values are shown for control prior to infusion (C Lover 3 hours of infusion and 0.5 hour (PI) after the end of infusion. FIGURE
CHEST 71: 2. FEBRUARY, 1977 SUPPLEMENT
Role of the Autonomic Nervous System and Pulmonary Artery Receptors in Production of Experimental Pulmonary Hypertension * Craig E. lurt1Uch,Ph.D.;"" lame. A. lengo, MD.;t and Michael M. Lab, M.D., F.C.C.P.;
R
ecently. we published evidence \..-htch demonstrates that acute' or chronic- balloon distention of the main pulmonary artery results in a significant elevation
I"~ noo~ " 900
~700
in the pulmonary artery pressure measured distal to the halloon. This pulmonary hypertension can occur in the
r.....
;
':-500 300
~12l
~
J::F (" c/o
,: ~~"
0.$
1
HOURS
2
of
INFUSION
~
0.5
METIIODS
PI
FIGl:RE 4. Data from continuous infusion of 0.10 to 0.15 mg kJ!; hr of glucagon in (j (cakes with chronic hypoxic pulmonary hypertension after 4 to 6 weeks at 3.400 m. See legend, Figure 1. for definition of symbols. Values are shown for control prior to infusion (C). over ,) hours of infusion and 0.5 hour (PI) after the end of infusion.
tially depressed hy chronic hypoxia. Therapeutic USt' of glucagon in congestive right heart failure due to hypoxic pulmonary hypertension may be
indicated; however, there was no evidence to suggest our calves had right heart failure and clinical trials using glucagon in human patients with cor pulmonale have not been uniformly successful.'
::~~I~'~~~~I~cJ~:GI T~t~li~lu~aOg~n ~~::= k~~at()~:;pli~a
hy the Eli Lilly Co" Indianapolis, Indiana. REFERE~C:ES
Levey GS, Epstein SE: Activation of adenyl cyclase by glucagon in eat and human heart. Cire Res 24: 151. 1969 2 Butcher R''". Sutherland E"'; Adenosine 3'. 5'~ph()sphate in biological materials. J Biol Chern 2.37:1z.4..c1, 1962 .1 Ro\~ GG: Systemic and c-oronary effects of glucagon. Am J Cardiel 25:670. 1970
4 Xamm DH, Leader JP: Occurrence and function of cyclic nucleottdes in blood vessels. Blood vessels 13:24, 1976 .3 Kirsh ~l~I, Kahn DR. Lucchesi B, et al: Effect of glucagon on pulmonary vasc-ular resistance. Surgery 70:439, 1971 6 Grover RF. Heeves JT. \ViII DB:. et al: Pulmonary vaseconstriction in steers at high altitude. J Appl Phystol IS:.5fi7. 19fn 7 Kones H]. Phillips JH: Glucagon: Present status in cardiavascular disease. Clin Pharmacol Therap 12:·l2i. Wil
CHEST 71: 2, FEBRUARY, 1977 SUPPLEMENT
absence of significant change in right ventricular enddiastolic pressure, aortic pressure and cardiac output. t Since balloon occlusion of one major branch of the pulmonary artery did not elevate pulmonary artery pressure/ a reflex mechanism was postulated to be responsible for the observed pulmonary hypertension. The purpose of this study was to investigate the role of the autonomic nervous system in the production of the proposed experimental pulmonary hypertension reflex.
These studies were conducted in 28 adult mongrel dogs of both sexes weighing between 18 and 24 kg. Dogs were prepared with aortic catheters and pulmonary artery triple lumen balloon catheters and either studied immediately while still anesthetized with sodium pentobarbital (.'30 mgl kg \ or allowed a recovery period of 8 to 14 days before being studied in the conscious state. The specially designed triple lumen balloon catheter and the technique for this animal preparation have been previously described.t-! Briefly, the catheter was Inserted through the jugular vein and the tip wedged under fluoroscopic control in a small branch of the pulmonary artery. wedging the tip of the catheter in a small pulmonary artery gave stability to the balloon in the main pulmonary artery during repeated inflation and deflation. From side lumens in this catheter, pressures were measured proximal to the pulmonary arterial balloon in the right ventricle and distal to the balloon in the main pulmonary artery. We have demonstrated angiographically that during balloon inflation, the pulmonary artery is distended by blood Rowing around the partially inflated balloon.' Afferent nerve pathways were evaluated by surgical denervation of the pulmonary artery wall, chemical blockade by lidocaine infiltration of the pulmonary artery wall. and bilateral cervical vagotomy. Surgical denervation of the pulmonary artery was accomplished by the following technique. Following left thoracotomy. the pulmonary artery and its major brunches were isolated and mobilized free from surrounding tissues. The subsequent removal of deep adventitial "From Harbor General Hospital, University of California Los Angeles SdlOOI of Med.cme. Torrance. This research was supported hy OO:\IH grant HL 18:l71~OI YIP. t'IH grant x». F22 HL 0159.3~02 cv.v, and :AI-lA,4GL:\;\ grant '0,511. Repri!lt rt'qucsls: Dr. iuratsch: Harbor Ceneral HO.\'IJital. 100 U"est Carson. Torrance. Caliiornia 90.5Of.)
'0.
19TH ASPEN LUNG CONFERENCE 265
Glucogon
3mg
160
.=E
.:a
140 120 100 110 100
90
Glucagon and Aminophylline as Pulmonary Vasodilators in the Calf with Hypoxic Pulmonary Hypertension *
..
80
:r
'10
E E
60 SO
40 30
Cerakl E. Bisuard, D.V.M., and James A. lVill, D.V.M.
T
he cardiovascular actions of glucagon and aminophylline han> been related to increasing intracellular levels of 3'5' cyclic adenosine monophosphate (cA~IP). The mode of activity of the ;2 agents differs: glucagon increases cA~1P bv increasing: the activitv of adenvlcyclase.' while ~inophylline and other methyl xanthines increase cAMP hy inhibiting phospbodicsterase" which is the enzyme which breaks down cA~fP to 5' A\IP. Some of the effects of increasing intracellular cA\fP are poteutiallv beneficial in certain cardiovascular diseases. These effects would include a positive inotropic and chronotropic' activity along with relaxation of contracted vascular smooth muscle.":' Wo wished to test the hypothesis that these 2 agents, glucagon and aminophylline operating by separate mechanisms to increase cA~lP, will reduce hypoxic pulmonary vasoconstriction. Calves were selected for this study because chronic airway hypoxia produces SIlS~ rained pulmonary hypertension which may lead to cor pulmonale (Brisket disease}." Furthermore. pulmonary hypertension is due to pulmonary vasoconstriction, and this is a reversible process as demonstrated by the fact that when chronic hypoxia is relieved, the vasoconstriction disappears and there is reversal of the pulmonary hypertension. Thus, cattle at high altitude provide an ideal situation for testing the action of potential pulmonary vasodilators. One additional advantage of the calf is that one may study these animals in the uvvakc, unsedated state, thus eliminating the effects of anesthesia on results ohtuined. Five calves were studied after 4 weeks of exposure at an altitude of 3,400 m (PH 510 mm Ilg). At this time, all calves had developed hypoxic pulmonary hypertension. At different times the calves were given either a single intravenous injection of aminophylline (5 mgkg) or a single intravenous injection of glucagon (3 mg). "From the L'niversitv of wtsconstn, Madison. Reprint request_\: ti« Bisgard. "eterinary Science Denartment. Unicersitn of '\·i.\'cDtlsin, Madison .53706
CHEST 71: 2, FEBRUARY. 1977 SUPPLEMENT
20
1~~~-' ; "'0
200
- -'- ...
~._._
•. _._._._.-._ ..
100
11.0 lO.O
...E
!
9.0
B.O 7.0 6.0 51015202530
40
MINUTES AnER INJECTION FIGL'RE 1. Data from bolus intravenous injection of 3 mg of glucagon. Solid circles and lines represent the data from 5 calves at 3,400 m. Vertical bars are cr; I SE~f. Open circles and dashed lines are data from 2 calves studied at sea level. C designates control prior to drug injection. HR = heart rate, P;;;, = mean aortic blood pressure, Pf:\ ::::: mean pulmonary arterial pressure, TPuR :.= total pulmonary vascular reststance. CI :;:: cardiae index.
Glucagon (Fig 1) caused a significant fall in total pulmonary vascular resistance (TPuR) brought about by both an increase in cardiac output (Cl ) and a fall in mean pulmonary arterial pressure (Pi'].) which were sustained for at least 20 minutes (control Pi'A ~ 64 rom Hg, minimum PI':, = 45 mm II~, P < O.O.?). Total peripheral resistance (TPeR) and mean aortic pressure (P,m) were also reduced while heart rate was significantly elevated by the bolus injection of glucagon. The pattern of response was similar at sea level except that TPuR and Pi':", were not altered.
19TH ASPEN LUNG CONFERENCE 263
AMINOPHYlllINI
In the sea level study no change in Pp-::'\ occurred, while there was a large decrease in the chronically hypoxic calves (control Pi':\ :::; H3 mm H~, average infusion Pi'A -- 46 mm lIg, P < 0.(1). Accordingly. TPuR was reduced by a larger magnitude in studies at 3,400 m as compared to sea level. There were no changes in arterial blood gases or acid-base balance induced by glucagon. Wtth the exception of heart rate changes in the altitude calves actions of glucagon were sustained throughout the period of infusion. In summary both glucagon and aminophylline caused reductions in TPuR. but with glucagon this was brought about by hoth an increase in CI and a fall in Pp:"\ while with aminophylline this occurred primarily by a reduction in pp\. Our data support our hypothesis that both aminophylline and glucagon are vasodilators in the presence of chronic hypoxic pulmonary vasoconstriction. The increased CI with glucagon in these calves was probably related to the knO\\11 positive' inotropic and chronotropic effects of this agent. The comparable increases in CI between spa level and high altitude indicates that chronic hypoxia does not depress the inotropic effect of glucagon. However. the reduction in maximum heart rate and failure to sustain a rapid heart rate during glucagon infusion in the chronically hypoxic calves suggests that chronotropic effects of glucagon may be par-
SmgJkg
140
.~
120
.ii 100
160 140
120 100
160
.~
S.O
140 120
A
c
,5 ~l.a~1 ,1
Jnutes
M)
100
15 1
80
after injeot'iCM"l
FI(;Ul\E2. Data from bolus intravenous injection of 5 mg kz of aminophylline. See legend, Figure 1, for definition of svmbols.
Aminophylline (Fig 2) injection caused a transient rise in heart rate and P;w while PP1 fell (control PF,\ 68 mm Hg, minimum Pj>A 51 mm Hg, P < 0.0.5). Maximal effects of pressures and heart rate occurred within the first minute of infusion of aminophylline and the reduction in pr;\ was sustained for only 10 minutes after infusion. TPuR decreased by a fall in Pp:\ with little change in CI. 1':0 changes in blood gases or acidbase balance were induced by either drug. In a second set of experiments 6 calves were studied at sea level and after 4 to 6 weeks at 3,400 m prior to and during a 3 hour infusion of glucagon at the rate of 0,10 to 0.15 mgvkgthr (Fig 3 and 4). Significant increases in heart rate occurred in both sea level and altitude studies; however, in the chronically hypoxic calves the increase in heart rate was significantly less than in sea level calves (mean maximum heart rate at sea level :::; 160 beats per minute, vs 134 beats per minute at high altitude) and was not sustained throughout infusion as it was in sea level studies. The increase in CI and decreases in P AO were comparable in sea level and high altitude studies.
=
264
=
19TH ASPEN LUNG CONFERENCE
10.0 M
0.0
C,
E
~
..0 7••
•. 0
c
LI.
0.5 HOURS of
~
INFUSiON
0.5 PI
3. Data from continuous infusion of 0.10 to 0.15 mgk~ .hr of glucagon in.6 calves at sea level. See legend. Figure 1, 'for definition of symbols, Values are shown for control prior to infusion (C Lover 3 hours of infusion and 0.5 hour (PI) after the end of infusion. FIGURE
CHEST 71: 2. FEBRUARY, 1977 SUPPLEMENT
Role of the Autonomic Nervous System and Pulmonary Artery Receptors in Production of Experimental Pulmonary Hypertension * Craig E. lurt1Uch,Ph.D.;"" lame. A. lengo, MD.;t and Michael M. Lab, M.D., F.C.C.P.;
R
ecently. we published evidence \..-htch demonstrates that acute' or chronic- balloon distention of the main pulmonary artery results in a significant elevation
I"~ noo~ " 900
~700
in the pulmonary artery pressure measured distal to the halloon. This pulmonary hypertension can occur in the
r.....
;
':-500 300
~12l
~
J::F (" c/o
,: ~~"
0.$
1
HOURS
2
of
INFUSION
~
0.5
METIIODS
PI
FIGl:RE 4. Data from continuous infusion of 0.10 to 0.15 mg kJ!; hr of glucagon in (j (cakes with chronic hypoxic pulmonary hypertension after 4 to 6 weeks at 3.400 m. See legend, Figure 1. for definition of symbols. Values are shown for control prior to infusion (C). over ,) hours of infusion and 0.5 hour (PI) after the end of infusion.
tially depressed hy chronic hypoxia. Therapeutic USt' of glucagon in congestive right heart failure due to hypoxic pulmonary hypertension may be
indicated; however, there was no evidence to suggest our calves had right heart failure and clinical trials using glucagon in human patients with cor pulmonale have not been uniformly successful.'
::~~I~'~~~~I~cJ~:GI T~t~li~lu~aOg~n ~~::= k~~at()~:;pli~a
hy the Eli Lilly Co" Indianapolis, Indiana. REFERE~C:ES
Levey GS, Epstein SE: Activation of adenyl cyclase by glucagon in eat and human heart. Cire Res 24: 151. 1969 2 Butcher R''". Sutherland E"'; Adenosine 3'. 5'~ph()sphate in biological materials. J Biol Chern 2.37:1z.4..c1, 1962 .1 Ro\~ GG: Systemic and c-oronary effects of glucagon. Am J Cardiel 25:670. 1970
4 Xamm DH, Leader JP: Occurrence and function of cyclic nucleottdes in blood vessels. Blood vessels 13:24, 1976 .3 Kirsh ~l~I, Kahn DR. Lucchesi B, et al: Effect of glucagon on pulmonary vasc-ular resistance. Surgery 70:439, 1971 6 Grover RF. Heeves JT. \ViII DB:. et al: Pulmonary vaseconstriction in steers at high altitude. J Appl Phystol IS:.5fi7. 19fn 7 Kones H]. Phillips JH: Glucagon: Present status in cardiavascular disease. Clin Pharmacol Therap 12:·l2i. Wil
CHEST 71: 2, FEBRUARY, 1977 SUPPLEMENT
absence of significant change in right ventricular enddiastolic pressure, aortic pressure and cardiac output. t Since balloon occlusion of one major branch of the pulmonary artery did not elevate pulmonary artery pressure/ a reflex mechanism was postulated to be responsible for the observed pulmonary hypertension. The purpose of this study was to investigate the role of the autonomic nervous system in the production of the proposed experimental pulmonary hypertension reflex.
These studies were conducted in 28 adult mongrel dogs of both sexes weighing between 18 and 24 kg. Dogs were prepared with aortic catheters and pulmonary artery triple lumen balloon catheters and either studied immediately while still anesthetized with sodium pentobarbital (.'30 mgl kg \ or allowed a recovery period of 8 to 14 days before being studied in the conscious state. The specially designed triple lumen balloon catheter and the technique for this animal preparation have been previously described.t-! Briefly, the catheter was Inserted through the jugular vein and the tip wedged under fluoroscopic control in a small branch of the pulmonary artery. wedging the tip of the catheter in a small pulmonary artery gave stability to the balloon in the main pulmonary artery during repeated inflation and deflation. From side lumens in this catheter, pressures were measured proximal to the pulmonary arterial balloon in the right ventricle and distal to the balloon in the main pulmonary artery. We have demonstrated angiographically that during balloon inflation, the pulmonary artery is distended by blood Rowing around the partially inflated balloon.' Afferent nerve pathways were evaluated by surgical denervation of the pulmonary artery wall, chemical blockade by lidocaine infiltration of the pulmonary artery wall. and bilateral cervical vagotomy. Surgical denervation of the pulmonary artery was accomplished by the following technique. Following left thoracotomy. the pulmonary artery and its major brunches were isolated and mobilized free from surrounding tissues. The subsequent removal of deep adventitial "From Harbor General Hospital, University of California Los Angeles SdlOOI of Med.cme. Torrance. This research was supported hy OO:\IH grant HL 18:l71~OI YIP. t'IH grant x». F22 HL 0159.3~02 cv.v, and :AI-lA,4GL:\;\ grant '0,511. Repri!lt rt'qucsls: Dr. iuratsch: Harbor Ceneral HO.\'IJital. 100 U"est Carson. Torrance. Caliiornia 90.5Of.)
'0.
19TH ASPEN LUNG CONFERENCE 265