Enzyme inhibition in colorectal surgery
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Br. J. Surg. Vol. 63 (1976) 23-24 Enzyme inhibition in colorectal surgery" PETER DELANEY AND DENIS LALORI. SUMMARY Anastomotic dehiscence is particularly common after low anterior resection of the rectum. The enzyme collagenase is largely responsible for this high compli- cation rate. Inhibition of this enzyme in an experimental model produced significantly stronger colonic anasto- moses. There may be a place for such an inhibitor in clinical surgery. THE clinical problem of anastomotic failure in bowel surgery is an ever present one. At various times the failure of anastomoses has been explained by a multitude of factors-hypoxia, hypovolaemia, mal- nutrition, systemic steroids, poor technique (inade- quate blood supply, tension on suture line, failure to invert), local infection and basic pathology, whether inflammatory or neoplastic. Nowhere is anastomotic dehiscence more common than in low anterior resection of the rectum, where leakage about the suture line has been estimated at between 5 and 30 per cent in different series. In 1969 the extent of this problem was highlighted by Goligher et al. in a meticulous review of a series of low anterior resections. The incidence of anastomotic failure was 67 per cent. While recognizing that all the above factors may play a part in the aetiology of anastomotic failure, there is now ample evidence to suggest a biochemical basis for this complication (Hawley et al., 1970). The strength of an anastomosis depends on the amount of mature collagen in the submucosal layer. This fact was realized by Halsted as long ago as 1887 when he based his anastomotic technique on the submucosal layer. The collagen molecule, with its triple helical structure, is a highly resistant substance. General tissue proteases have little effect on it and collagenolysis is brought about by the enzyme collagenase. Until 1962, when Gross and Lapiere succeeded in identifying a collagen- ase from cultures of tadpole tails, it was felt that enzymes of mammalian origin did not affect native collagen. An enormous amount of research has since been carried out on this subject and now collagenases can be identified in many tissues-healing wounds, synoviai fluid in rheumatoid arthritis, bone, poly- morphonuclear leucocytes, tumour tissue and many others. Under normal circumstances the collagen pool is in a state of dynamic equilibrium. Mature collagen is lysed by collagenase and new collagen is synthesized by fibroblasts. The activity of mammalian colla- genases is inhibited by factors normally present in the serum and specifically by the a-Zmacroglobulin fraction which is also an anti-trypsin (Werb et al., 1974). In 1972 Sakomotoet al. showed that serum prepared free of trypsin inhibitors failed to inhibit collagenase activity. Likewise, the activity of a mouse bone collagenase system (in the presence of a concentration of serum which would otherwise have inhibited it) was restored by the addition of trypsin. There is a number of explanations for these findings but one possibility is that the factors responsible for the inhibition of trypsin and collagenase may be identical. Gastro-intestinal collagenase Collagenase activity varies throughout the gastro- intestinal tract. Experimental work has shown that the level of this activity is lowest in the stomach and greatest in the distal colon. The site of an anastomosis shows increased collagenolysis with an associated decrease in mature collagen (Cronin et al., 1968). This postoperative increase in connective tissue breakdown is most marked when the anastomosis is in the lower colon. Local infection at the site of anastomosis further increases collagenolytic activity (Hawley et al., 1970). Table I: BURSTING PRESSURES OF COLONIC ANASTOMOSES 4-Day group 7-Day group Control Trasylol Control Trasylol 50 15 35 80 60 75 35 95 60 85 40 100 60 90 70 I 00 65 90 95 100 70 95 95 110 75 100 100 120 95 120 105 125 100 120 110 130 100 150 120 150 Mean 73.5 100.0 80.5 111.0 t= 2.80 t = 3.614 d.f.= 18 d.f.= 18 0.02 >P> 0.01 0.005 >P> 0.001 Results given in mm Hg. Collagenase, therefore, would appear to be a factor in anastomotic dehiscence. By inhibiting this enzyme it should be possible to produce a stronger anasto- mosis. Trypsin and collagenase, as previously stated, may be inhibited by similar factors. An experimental model was set up in which a known anti-trypsin (Trasylol) was used in an attempt to inhibit collagenase and thereby decrease the incidence of anastomotic breakdown. * Based on a paper read to the Surgical Research Society in July 1974. t Mater Hospital, and Department of Experimental Surgery, University College, Dublin. 23
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Transcript of Enzyme inhibition in colorectal surgery
Br. J. Surg. Vol. 63 (1976) 23-24
Enzyme inhibition in colorectal surgery" P E T E R D E L A N E Y A N D DENIS LALORI.
SUMMARY Anastomotic dehiscence is particularly common after low anterior resection of the rectum. The enzyme collagenase is largely responsible for this high compli- cation rate. Inhibition of this enzyme in an experimental model produced significantly stronger colonic anasto- moses. There may be a place for such an inhibitor in clinical surgery.
THE clinical problem of anastomotic failure in bowel surgery is an ever present one. At various times the failure of anastomoses has been explained by a multitude of factors-hypoxia, hypovolaemia, mal- nutrition, systemic steroids, poor technique (inade- quate blood supply, tension on suture line, failure to invert), local infection and basic pathology, whether inflammatory or neoplastic.
Nowhere is anastomotic dehiscence more common than in low anterior resection of the rectum, where leakage about the suture line has been estimated at between 5 and 30 per cent in different series. In 1969 the extent of this problem was highlighted by Goligher et al. in a meticulous review of a series of low anterior resections. The incidence of anastomotic failure was 67 per cent.
While recognizing that all the above factors may play a part in the aetiology of anastomotic failure, there is now ample evidence to suggest a biochemical basis for this complication (Hawley et al., 1970). The strength of an anastomosis depends on the amount of mature collagen in the submucosal layer. This fact was realized by Halsted as long ago as 1887 when he based his anastomotic technique on the submucosal layer. The collagen molecule, with its triple helical structure, is a highly resistant substance. General tissue proteases have little effect on it and collagenolysis is brought about by the enzyme collagenase. Until 1962, when Gross and Lapiere succeeded in identifying a collagen- ase from cultures of tadpole tails, it was felt that enzymes of mammalian origin did not affect native collagen. An enormous amount of research has since been carried out on this subject and now collagenases can be identified in many tissues-healing wounds, synoviai fluid in rheumatoid arthritis, bone, poly- morphonuclear leucocytes, tumour tissue and many others.
Under normal circumstances the collagen pool is in a state of dynamic equilibrium. Mature collagen is lysed by collagenase and new collagen is synthesized by fibroblasts. The activity of mammalian colla- genases is inhibited by factors normally present in the serum and specifically by the a-Zmacroglobulin fraction which is also an anti-trypsin (Werb et al., 1974).
In 1972 Sakomotoet al. showed that serum prepared free of trypsin inhibitors failed to inhibit collagenase activity. Likewise, the activity of a mouse bone collagenase system (in the presence of a concentration of serum which would otherwise have inhibited it) was restored by the addition of trypsin. There is a number of explanations for these findings but one possibility is that the factors responsible for the inhibition of trypsin and collagenase may be identical.
Gastro-intestinal collagenase Collagenase activity varies throughout the gastro- intestinal tract. Experimental work has shown that the level of this activity is lowest in the stomach and greatest in the distal colon. The site of an anastomosis shows increased collagenolysis with an associated decrease in mature collagen (Cronin et al., 1968). This postoperative increase in connective tissue breakdown is most marked when the anastomosis is in the lower colon. Local infection at the site of anastomosis further increases collagenolytic activity (Hawley et al., 1970).
Table I: BURSTING PRESSURES OF COLONIC ANASTOMOSES
4-Day group 7-Day group
Control Trasylol Control Trasylol
50 15 35 80 60 75 35 95 60 85 40 100 60 90 70 I 00 65 90 95 100 70 95 95 110 75 100 100 120 95 120 105 125
100 120 110 130 100 150 120 150
Mean 73.5 100.0 80.5 111.0 t = 2.80 t = 3.614 d.f.= 18 d.f.= 18
0.02 >P> 0.01 0.005 > P > 0.001
Results given in mm Hg.
Collagenase, therefore, would appear to be a factor in anastomotic dehiscence. By inhibiting this enzyme it should be possible to produce a stronger anasto- mosis. Trypsin and collagenase, as previously stated, may be inhibited by similar factors. An experimental model was set up in which a known anti-trypsin (Trasylol) was used in an attempt to inhibit collagenase and thereby decrease the incidence of anastomotic breakdown.
* Based on a paper read to the Surgical Research Society in July 1974. t Mater Hospital, and Department of Experimental Surgery, University College, Dublin.
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Peter Delaney and Denis Lalor
Experimental protocol Forty New Zealand white rabbits were used. These were divided into two groups of 20. The composition of the groups with regard to age, sex and weight was similar. A colonic anastomosis was constructed in each rabbit. One group was sacrificed at 4 days and the other at 7 days, and the bursting pressure of each anastomosis was measured. Half of each group was used as controls while the other half was given Trasylol (100 000 units daily subcutaneously in three divided doses).
Results The average bursting pressure of the Trasylol subgroup (Table Z) was 36 per cent higher in the 4-day group (0.02>P>0.01) and 37 per cent higher in the 7-day group (0.005 > Pz 0.001).
Conclusion These results are significant. There may be a place for collagenase inhibitors in clinical practice. It is suggested that the low anterior resection with its high incidence of anastomotic failure would be such a situation.
References CRONIN D., JACKSON D. S. and DUNPHY J. E. (1968)
Changing bursting strength and collagen content in the healing colon. Surg. Gynecol. Obstet. 126, 747-753.
GOLIGHER J. c., GRAHAM N. G. and DE DOMBAL F. T. (1969) Anastomotic dehiscence after anterior resection of the rectum. Br. J. Surg. 56, 692.
GROSS J. and LAPIERE c. M. (1962) Collagenolytic activity in amphibian tissues-a tissue culture assay. Proc. Natl Acad. Sci. USA 48, 1014-1022.
HALSTED w. s. (1887) Circular suture of the intestine- an experimental study. Am. J . Med. Sci. 94, 436-461.
HAWLEY P. R., HUNT T. K. and DUNPHY J. E. (1970) The aetiology of colonic anastomotic leaks. Proc. R. SOC. Med. 63 (Suppl.), 28.
SAKOMOTO s., GOLDLABER P. and GLINCHER M. J. (1972) Maintenance of mouse bone collagenase activity in the presence of serum protein by addition of trypsin. Proc. SOC. Exp. Biol. Med. 139, 1038- 1041.
WERB z., BURLEIGH M. c., BARRETT A. J. and STARKEY P. M. (1974) The interaction of alpha 2-macro- globulin with proteinazes. Biochern. J . 139, 359-368.
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