Could upright-rows replace lateral-pulldowns, this would be from time to time when not getting to the gym.
Upright feels saver for the back and more loadable than bentover-rows.
Upright rows target the musculature of the upper back (middle/upper fibers of trapezius, etc.), in contrast to Lat-Pulldowns which active the Latissimus Dorsi to a greater degree. Bent over rows are fantastic for the musculature of the upper back and lats.
If you are looking for a substitute for lat pulldowns I would encourage you to replace them all together in favor of chin/pullup variations. There is no comparison between chins/pullups and lat pull downs.
Substitutes should exist in the same plane of movement (i.e., lat pulldowns and chins are frontal plane movements, whereas rows are a sagittal plane movement).
James
I think you guys may be forgetting what happens in an upright row structurally. The upright row combines humeral internal rotation with shoulder abduction and creates an impingement on the rotator cuff. There are better alternatives to target the upper back and deltoids that won’t sacrifice joint integrity.
If you are doing any olympic lifts upright rows are not necessary, unless you want a trapezius the size of a house. 
Me and my shoulder’s second this. Upright rows, the great pain inducer!
I also agree on pullups, they are a great lat exercise.
Ron