218 
PULMONARY MODELS 
cells. Following destruction of the endothelial 
cells the basal laminae of the alveolar walls 
were ruptured, permitting hemorrhage into 
the alveolar lumen. Thus well-defined morpho- 
logic criteria for assessing damage to the blood- 
air barrier have been established. 
.1 
RESULTS OF TRYPTOPHAN ADMINISTRATION 
Since so-called acute pulmonary emphysema 
occurs in the ox soon after a drastic change in 
feed, the possibility of a metabolite from the 
digestive tract relating to the pulmonary pathol- 
ogy has received attention.**^'^'^° Two routes 
have been suggested: (1) a compound could be 
absorbed from the stomach or intestine and 
follow a hematogenous route to the lungs ; and 
(2) a gaseous metabolite may be eructated from 
the rumen and inhaled.'* Three to seven times as 
much eructated ruminal gas follows this route 
as that which is eructated immediately to the 
outside. 1^ In order to correlate the pathophysiol- 
ogy of acute bovine pulmonary emphysema to 
morphologic changes, it is essential to establish 
a reliable experimental method for provoking 
the disease. Experimental induction of an acute 
respiratory syndrome resembling bovine pul- 
monary emphysema by the intraruminal ad- 
ministration of d, 1-tryptophan has been re- 
ported.^'''^° We attempted to induce the 
syndrome by this method. 
Eight cows (6 Herefords, 1 Brown Swiss- 
Jersey crossbred and 1 Holstein-Friesian) five 
to over 15 years of age and in varying physical 
condition were fed a diet of grass hay at least 30 
days prior to the intraruminal administration 
of d,l- or 1-tryptophan. The major plants in the 
grass hay were timothy (Phleum sp.), bluegrass 
(Poa sp.), redtop (Agrostis sp.), hairgrass 
(Deschampsia sp.), and a sedge (Carex sp.). 
Dosages varied from 0.7 g of d,l-tryptophan* to 
0.35 g, 0.525 g or 0.7 g of 1-tryptophan** per 
kilogram of body weight. The total mass of 
tryptophan (150 to 300 g) was suspended in 6 
to 8 liters of water, and the suspension was 
pumped into the rumen through a stomach tube. 
The cows were permitted continued access to 
hay and water. 
* Nutritional Biochemical Corp., Cleveland, Ohio. 
** Sigma Chemical Co., St. Louis, Missouri. 
Previous to the administration of the trypto- 
phan, a common carotid artery was exteriorized 
so that arterial as well as jugular blood samples 
could be collected for analysis of pH, P( 02, P02, 
oxygen saturation and hemoglobin content. The 
hematologic determinations and pulmonary 
function tests were performed before trypto- 
phan was given and at intervals following ad- 
ministration. Tidal volumes were recorded 
utilizing a face mask with an attached pneu- 
motachometer connected to a transducer. An 
intraesophageal tube with a terminal cuff was 
used to ascertain transthoracic pressure. A 
catheter was passed through a jugular vein and 
the right heart to the pulmonary trunk where 
pulmonary arterial pressure was relayed by 
means of a transducer. The transducers were 
monitored on a Sanborn recorder. 
Following the administration of tryptophan, 
the cows were observed for clinical signs, and 
hematologic and pulmonary parameters were de- 
termined sporadically for from one to five days. 
Results were essentially negative in that the 
classic signs of acute bovine pulmonary emphy- 
sema were not observed in any of the eight 
cows used in the experiments. One physiologic 
parameter, the pulmonary arterial pressure, 
varied significantly in three cows. A dose of 
0.7 g d, 1-tryptophan per kg of body weight was 
given to a six-year-old Hereford cow (A205, 
Table I). There was no physiologic response. 
After three weeks a subsequent dose of 0.35 g 
Table I. — Intraruminal Administration of Tryptophan 
to Hereford Cows 
Cow Age 
Dose/Kg Body Weight 
Time 
(hrs) 
Pul. Art 
Pres. 
(mm Hg) 
A205 6 yr 
Pretreatment 
28 
0.7 g d,l-ti'yptophan 
24 
25 
48 
25 
72 
25 
96 
24 
0.35 e 1-tryptophan 
Pretreatment 
23 
72 
50 
96 
32 
120 
23 
A201 6 yr 
Pretreatment 
20 
0.7 g 1-tryptophan 
48 
27 
72 
28 
96 
50 
120 
60 
480 15+ yr 
Pretreatment 
70 
0.525 g 1-tryptophan 
24 
115 
72 
62 
